From 57b10c06925d0bdf6ffb38488ee908f085109e95 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Thu, 4 Jul 2019 19:12:15 +0300
Subject: Move config, dist, test, and install modules into library

---
 libbuild2/test/script/builtin.cxx                  | 1979 +++++++++++
 libbuild2/test/script/builtin.hxx                  |   74 +
 .../script/lexer+command-expansion.test.testscript |  248 ++
 .../test/script/lexer+command-line.test.testscript |  208 ++
 .../script/lexer+description-line.test.testscript  |   33 +
 .../test/script/lexer+first-token.test.testscript  |   97 +
 .../test/script/lexer+second-token.test.testscript |   68 +
 .../script/lexer+variable-line.test.testscript     |   28 +
 .../test/script/lexer+variable.test.testscript     |   70 +
 libbuild2/test/script/lexer.cxx                    |  551 ++++
 libbuild2/test/script/lexer.hxx                    |   94 +
 libbuild2/test/script/lexer.test.cxx               |   85 +
 .../test/script/parser+cleanup.test.testscript     |   58 +
 .../test/script/parser+command-if.test.testscript  |  548 ++++
 .../script/parser+command-re-parse.test.testscript |   12 +
 .../test/script/parser+description.test.testscript |  486 +++
 .../test/script/parser+directive.test.testscript   |   74 +
 libbuild2/test/script/parser+exit.test.testscript  |   27 +
 .../test/script/parser+expansion.test.testscript   |   36 +
 .../script/parser+here-document.test.testscript    |  213 ++
 .../test/script/parser+here-string.test.testscript |   19 +
 .../test/script/parser+include.test.testscript     |  104 +
 .../test/script/parser+pipe-expr.test.testscript   |  133 +
 .../test/script/parser+pre-parse.test.testscript   |   23 +
 .../test/script/parser+redirect.test.testscript    |  356 ++
 libbuild2/test/script/parser+regex.test.testscript |  223 ++
 .../test/script/parser+scope-if.test.testscript    |  554 ++++
 libbuild2/test/script/parser+scope.test.testscript |  280 ++
 .../script/parser+setup-teardown.test.testscript   |  151 +
 libbuild2/test/script/parser.cxx                   | 3451 ++++++++++++++++++++
 libbuild2/test/script/parser.hxx                   |  250 ++
 libbuild2/test/script/parser.test.cxx              |  245 ++
 libbuild2/test/script/regex.cxx                    |  440 +++
 libbuild2/test/script/regex.hxx                    |  703 ++++
 libbuild2/test/script/regex.ixx                    |   35 +
 libbuild2/test/script/regex.test.cxx               |  302 ++
 libbuild2/test/script/runner.cxx                   | 1891 +++++++++++
 libbuild2/test/script/runner.hxx                   |  101 +
 libbuild2/test/script/script.cxx                   |  741 +++++
 libbuild2/test/script/script.hxx                   |  559 ++++
 libbuild2/test/script/script.ixx                   |   60 +
 libbuild2/test/script/token.cxx                    |   57 +
 libbuild2/test/script/token.hxx                    |   65 +
 43 files changed, 15732 insertions(+)
 create mode 100644 libbuild2/test/script/builtin.cxx
 create mode 100644 libbuild2/test/script/builtin.hxx
 create mode 100644 libbuild2/test/script/lexer+command-expansion.test.testscript
 create mode 100644 libbuild2/test/script/lexer+command-line.test.testscript
 create mode 100644 libbuild2/test/script/lexer+description-line.test.testscript
 create mode 100644 libbuild2/test/script/lexer+first-token.test.testscript
 create mode 100644 libbuild2/test/script/lexer+second-token.test.testscript
 create mode 100644 libbuild2/test/script/lexer+variable-line.test.testscript
 create mode 100644 libbuild2/test/script/lexer+variable.test.testscript
 create mode 100644 libbuild2/test/script/lexer.cxx
 create mode 100644 libbuild2/test/script/lexer.hxx
 create mode 100644 libbuild2/test/script/lexer.test.cxx
 create mode 100644 libbuild2/test/script/parser+cleanup.test.testscript
 create mode 100644 libbuild2/test/script/parser+command-if.test.testscript
 create mode 100644 libbuild2/test/script/parser+command-re-parse.test.testscript
 create mode 100644 libbuild2/test/script/parser+description.test.testscript
 create mode 100644 libbuild2/test/script/parser+directive.test.testscript
 create mode 100644 libbuild2/test/script/parser+exit.test.testscript
 create mode 100644 libbuild2/test/script/parser+expansion.test.testscript
 create mode 100644 libbuild2/test/script/parser+here-document.test.testscript
 create mode 100644 libbuild2/test/script/parser+here-string.test.testscript
 create mode 100644 libbuild2/test/script/parser+include.test.testscript
 create mode 100644 libbuild2/test/script/parser+pipe-expr.test.testscript
 create mode 100644 libbuild2/test/script/parser+pre-parse.test.testscript
 create mode 100644 libbuild2/test/script/parser+redirect.test.testscript
 create mode 100644 libbuild2/test/script/parser+regex.test.testscript
 create mode 100644 libbuild2/test/script/parser+scope-if.test.testscript
 create mode 100644 libbuild2/test/script/parser+scope.test.testscript
 create mode 100644 libbuild2/test/script/parser+setup-teardown.test.testscript
 create mode 100644 libbuild2/test/script/parser.cxx
 create mode 100644 libbuild2/test/script/parser.hxx
 create mode 100644 libbuild2/test/script/parser.test.cxx
 create mode 100644 libbuild2/test/script/regex.cxx
 create mode 100644 libbuild2/test/script/regex.hxx
 create mode 100644 libbuild2/test/script/regex.ixx
 create mode 100644 libbuild2/test/script/regex.test.cxx
 create mode 100644 libbuild2/test/script/runner.cxx
 create mode 100644 libbuild2/test/script/runner.hxx
 create mode 100644 libbuild2/test/script/script.cxx
 create mode 100644 libbuild2/test/script/script.hxx
 create mode 100644 libbuild2/test/script/script.ixx
 create mode 100644 libbuild2/test/script/token.cxx
 create mode 100644 libbuild2/test/script/token.hxx

(limited to 'libbuild2/test/script')

diff --git a/libbuild2/test/script/builtin.cxx b/libbuild2/test/script/builtin.cxx
new file mode 100644
index 0000000..ab57d4f
--- /dev/null
+++ b/libbuild2/test/script/builtin.cxx
@@ -0,0 +1,1979 @@
+// file      : libbuild2/test/script/builtin.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/test/script/builtin.hxx>
+
+#include <chrono>
+#include <locale>
+#include <ostream>
+#include <sstream>
+#include <cstdlib> // strtoull()
+
+#include <libbutl/regex.mxx>
+#include <libbutl/path-io.mxx>    // use default operator<< implementation
+#include <libbutl/fdstream.mxx>   // fdopen_mode, fdstream_mode
+#include <libbutl/filesystem.mxx>
+
+#include <libbuild2/context.hxx> // sched
+
+#include <libbuild2/test/script/script.hxx>
+
+// Strictly speaking a builtin which reads/writes from/to standard streams
+// must be asynchronous so that the caller can communicate with it through
+// pipes without being blocked on I/O operations. However, as an optimization,
+// we allow builtins that only print diagnostics to STDERR to be synchronous
+// assuming that their output will always fit the pipe buffer. Synchronous
+// builtins must not read from STDIN and write to STDOUT. Later we may relax
+// this rule to allow a "short" output for such builtins.
+//
+using namespace std;
+using namespace butl;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      using builtin_impl = uint8_t (scope&,
+                                    const strings& args,
+                                    auto_fd in, auto_fd out, auto_fd err);
+
+      // Operation failed, diagnostics has already been issued.
+      //
+      struct failed {};
+
+      // Accumulate an error message, print it atomically in dtor to the
+      // provided stream and throw failed afterwards if requested. Prefixes
+      // the message with the builtin name.
+      //
+      // Move constructible-only, not assignable (based to diag_record).
+      //
+      class error_record
+      {
+      public:
+        template <typename T>
+        friend const error_record&
+        operator<< (const error_record& r, const T& x)
+        {
+          r.ss_ << x;
+          return r;
+        }
+
+        error_record (ostream& o, bool fail, const char* name)
+            : os_ (o), fail_ (fail), empty_ (false)
+        {
+          ss_ << name << ": ";
+        }
+
+        // Older versions of libstdc++ don't have the ostringstream move
+        // support. Luckily, GCC doesn't seem to be actually needing move due
+        // to copy/move elision.
+        //
+#ifdef __GLIBCXX__
+        error_record (error_record&&);
+#else
+        error_record (error_record&& r)
+            : os_ (r.os_),
+              ss_ (move (r.ss_)),
+              fail_ (r.fail_),
+              empty_ (r.empty_)
+        {
+          r.empty_ = true;
+        }
+#endif
+
+        ~error_record () noexcept (false)
+        {
+          if (!empty_)
+          {
+            // The output stream can be in a bad state (for example as a
+            // result of unsuccessful attempt to report a previous error), so
+            // we check it.
+            //
+            if (os_.good ())
+            {
+              ss_.put ('\n');
+              os_ << ss_.str ();
+              os_.flush ();
+            }
+
+            if (fail_)
+              throw failed ();
+          }
+        }
+
+      private:
+        ostream& os_;
+        mutable ostringstream ss_;
+
+        bool fail_;
+        bool empty_;
+      };
+
+      // Parse and normalize a path. Also, unless it is already absolute, make
+      // the path absolute using the specified directory. Throw invalid_path
+      // if the path is empty, and on parsing and normalization failures.
+      //
+      static path
+      parse_path (string s, const dir_path& d)
+      {
+        path p (move (s));
+
+        if (p.empty ())
+          throw invalid_path ("");
+
+        if (p.relative ())
+          p = d / move (p);
+
+        p.normalize ();
+        return p;
+      }
+
+      // Builtin commands functions.
+      //
+
+      // cat <file>...
+      //
+      // Note that POSIX doesn't specify if after I/O operation failure the
+      // command should proceed with the rest of the arguments. The current
+      // implementation exits immediatelly in such a case.
+      //
+      // @@ Shouldn't we check that we don't print a nonempty regular file to
+      //    itself, as that would merely exhaust the output device? POSIX
+      //    allows (but not requires) such a check and some implementations do
+      //    this. That would require to fstat() file descriptors and complicate
+      //    the code a bit. Was able to reproduce on a big file (should be
+      //    bigger than the stream buffer size) with the test
+      //    'cat file >+file'.
+      //
+      // Note: must be executed asynchronously.
+      //
+      static uint8_t
+      cat (scope& sp,
+           const strings& args,
+           auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "cat");
+        };
+
+        try
+        {
+          ifdstream cin  (move (in),  fdstream_mode::binary);
+          ofdstream cout (move (out), fdstream_mode::binary);
+
+          // Copy input stream to STDOUT.
+          //
+          auto copy = [&cout] (istream& is)
+          {
+            if (is.peek () != ifdstream::traits_type::eof ())
+              cout << is.rdbuf ();
+
+            is.clear (istream::eofbit); // Sets eofbit.
+          };
+
+          // Path of a file being printed to STDOUT. An empty path represents
+          // STDIN. Used in diagnostics.
+          //
+          path p;
+
+          try
+          {
+            // Print STDIN.
+            //
+            if (args.empty ())
+              copy (cin);
+
+            // Print files.
+            //
+            for (auto i (args.begin ()); i != args.end (); ++i)
+            {
+              if (*i == "-")
+              {
+                if (!cin.eof ())
+                {
+                  p.clear ();
+                  copy (cin);
+                }
+
+                continue;
+              }
+
+              p = parse_path (*i, sp.wd_path);
+
+              ifdstream is (p, ifdstream::binary);
+              copy (is);
+              is.close ();
+            }
+          }
+          catch (const io_error& e)
+          {
+            error_record d (error ());
+            d << "unable to print ";
+
+            if (p.empty ())
+              d << "stdin";
+            else
+              d << "'" << p << "'";
+
+            d << ": " << e;
+          }
+
+          cin.close ();
+          cout.close ();
+          r = 0;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while creating/closing cin, cout or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // Make a copy of a file at the specified path, preserving permissions,
+      // and registering a cleanup for a newly created file. The file paths
+      // must be absolute. Fail if an exception is thrown by the underlying
+      // copy operation.
+      //
+      static void
+      cpfile (scope& sp,
+              const path& from, const path& to,
+              bool overwrite,
+              bool attrs,
+              bool cleanup,
+              const function<error_record()>& fail)
+      {
+        try
+        {
+          bool exists (file_exists (to));
+
+          cpflags f (
+            overwrite
+            ? cpflags::overwrite_permissions | cpflags::overwrite_content
+            : cpflags::none);
+
+          if (attrs)
+            f |= cpflags::overwrite_permissions | cpflags::copy_timestamps;
+
+          cpfile (from, to, f);
+
+          if (!exists && cleanup)
+            sp.clean ({cleanup_type::always, to}, true);
+        }
+        catch (const system_error& e)
+        {
+          fail () << "unable to copy file '" << from << "' to '" << to
+                  << "': " << e;
+        }
+      }
+
+      // Make a copy of a directory at the specified path, registering a
+      // cleanup for the created directory. The directory paths must be
+      // absolute. Fail if the destination directory already exists or
+      // an exception is thrown by the underlying copy operation.
+      //
+      static void
+      cpdir (scope& sp,
+             const dir_path& from, const dir_path& to,
+             bool attrs,
+             bool cleanup,
+             const function<error_record()>& fail)
+      {
+        try
+        {
+          if (try_mkdir (to) == mkdir_status::already_exists)
+            throw_generic_error (EEXIST);
+
+          if (cleanup)
+            sp.clean ({cleanup_type::always, to}, true);
+
+          for (const auto& de: dir_iterator (from,
+                                             false /* ignore_dangling */))
+          {
+            path f (from / de.path ());
+            path t (to / de.path ());
+
+            if (de.type () == entry_type::directory)
+              cpdir (sp,
+                     path_cast<dir_path> (move (f)),
+                     path_cast<dir_path> (move (t)),
+                     attrs,
+                     cleanup,
+                     fail);
+            else
+              cpfile (sp, f, t, false /* overwrite */, attrs, cleanup, fail);
+          }
+
+          // Note that it is essential to copy timestamps and permissions after
+          // the directory content is copied.
+          //
+          if (attrs)
+          {
+            path_permissions (to, path_permissions (from));
+            dir_time (to, dir_time (from));
+          }
+        }
+        catch (const system_error& e)
+        {
+          fail () << "unable to copy directory '" << from << "' to '" << to
+                  << "': " << e;
+        }
+      }
+
+      // cp [-p] [--no-cleanup]        <src-file>     <dst-file>
+      // cp [-p] [--no-cleanup] -R|-r  <src-dir>      <dst-dir>
+      // cp [-p] [--no-cleanup]        <src-file>...  <dst-dir>/
+      // cp [-p] [--no-cleanup] -R|-r  <src-path>...  <dst-dir>/
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      cp (scope& sp,
+          const strings& args,
+          auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "cp");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool recursive (false);
+          bool attrs (false);
+          bool cleanup (true);
+          for (; i != e; ++i)
+          {
+            const string& o (*i);
+
+            if (o == "-R" || o == "-r")
+              recursive = true;
+            else if (o == "-p")
+              attrs = true;
+            else if (o == "--no-cleanup")
+              cleanup = false;
+            else
+            {
+              if (o == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          // Copy files or directories.
+          //
+          if (i == e)
+            error () << "missing arguments";
+
+          const dir_path& wd (sp.wd_path);
+
+          auto j (args.rbegin ());
+          path dst (parse_path (*j++, wd));
+          e = j.base ();
+
+          if (i == e)
+            error () << "missing source path";
+
+          auto fail = [&error] () {return error (true);};
+
+          // If destination is not a directory path (no trailing separator)
+          // then make a copy of the filesystem entry at the specified path
+          // (the only source path is allowed in such a case). Otherwise copy
+          // the source filesystem entries into the destination directory.
+          //
+          if (!dst.to_directory ())
+          {
+            path src (parse_path (*i++, wd));
+
+            // If there are multiple sources but no trailing separator for the
+            // destination, then, most likelly, it is missing.
+            //
+            if (i != e)
+              error () << "multiple source paths without trailing separator "
+                       << "for destination directory";
+
+            if (!recursive)
+              // Synopsis 1: make a file copy at the specified path.
+              //
+              cpfile (sp,
+                      src,
+                      dst,
+                      true /* overwrite */,
+                      attrs,
+                      cleanup,
+                      fail);
+            else
+              // Synopsis 2: make a directory copy at the specified path.
+              //
+              cpdir (sp,
+                     path_cast<dir_path> (src), path_cast<dir_path> (dst),
+                     attrs,
+                     cleanup,
+                     fail);
+          }
+          else
+          {
+            for (; i != e; ++i)
+            {
+              path src (parse_path (*i, wd));
+
+              if (recursive && dir_exists (src))
+                // Synopsis 4: copy a filesystem entry into the specified
+                // directory. Note that we handle only source directories here.
+                // Source files are handled below.
+                //
+                cpdir (sp,
+                       path_cast<dir_path> (src),
+                       path_cast<dir_path> (dst / src.leaf ()),
+                       attrs,
+                       cleanup,
+                       fail);
+              else
+                // Synopsis 3: copy a file into the specified directory. Also,
+                // here we cover synopsis 4 for the source path being a file.
+                //
+                cpfile (sp,
+                        src,
+                        dst / src.leaf (),
+                        true /* overwrite */,
+                        attrs,
+                        cleanup,
+                        fail);
+            }
+          }
+
+          r = 0;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // echo <string>...
+      //
+      // Note: must be executed asynchronously.
+      //
+      static uint8_t
+      echo (scope&,
+            const strings& args,
+            auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        try
+        {
+          in.close ();
+          ofdstream cout (move (out));
+
+          for (auto b (args.begin ()), i (b), e (args.end ()); i != e; ++i)
+            cout << (i != b ? " " : "") << *i;
+
+          cout << '\n';
+          cout.close ();
+          r = 0;
+        }
+        catch (const std::exception& e)
+        {
+          cerr << "echo: " << e << endl;
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // false
+      //
+      // Failure to close the file descriptors is silently ignored.
+      //
+      // Note: can be executed synchronously.
+      //
+      static builtin
+      false_ (scope&, uint8_t& r, const strings&, auto_fd, auto_fd, auto_fd)
+      {
+        return builtin (r = 1);
+      }
+
+      // true
+      //
+      // Failure to close the file descriptors is silently ignored.
+      //
+      // Note: can be executed synchronously.
+      //
+      static builtin
+      true_ (scope&, uint8_t& r, const strings&, auto_fd, auto_fd, auto_fd)
+      {
+        return builtin (r = 0);
+      }
+
+      // Create a symlink to a file or directory at the specified path. The
+      // paths must be absolute. Fall back to creating a hardlink, if symlink
+      // creation is not supported for the link path. If hardlink creation is
+      // not supported either, then fall back to copies. If requested, created
+      // filesystem entries are registered for cleanup. Fail if the target
+      // filesystem entry doesn't exist or an exception is thrown by the
+      // underlying filesystem operation (specifically for an already existing
+      // filesystem entry at the link path).
+      //
+      // Note that supporting optional removal of an existing filesystem entry
+      // at the link path (the -f option) tends to get hairy. As soon as an
+      // existing and the resulting filesystem entries could be of different
+      // types, we would end up with canceling an old cleanup and registering
+      // the new one. Also removing non-empty directories doesn't look very
+      // natural, but would be required if we want the behavior on POSIX and
+      // Windows to be consistent.
+      //
+      static void
+      mksymlink (scope& sp,
+                 const path& target, const path& link,
+                 bool cleanup,
+                 const function<error_record()>& fail)
+      {
+        // Determine the target type, fail if the target doesn't exist.
+        //
+        bool dir (false);
+
+        try
+        {
+          pair<bool, entry_stat> pe (path_entry (target));
+
+          if (!pe.first)
+            fail () << "unable to create symlink to '" << target << "': "
+                    << "no such file or directory";
+
+          dir = pe.second.type == entry_type::directory;
+        }
+        catch (const system_error& e)
+        {
+          fail () << "unable to stat '" << target << "': " << e;
+        }
+
+        // First we try to create a symlink. If that fails (e.g., "Windows
+        // happens"), then we resort to hard links. If that doesn't work out
+        // either (e.g., not on the same filesystem), then we fall back to
+        // copies. So things are going to get a bit nested.
+        //
+        try
+        {
+          mksymlink (target, link, dir);
+
+          if (cleanup)
+            sp.clean ({cleanup_type::always, link}, true);
+        }
+        catch (const system_error& e)
+        {
+          // Note that we are not guaranteed (here and below) that the
+          // system_error exception is of the generic category.
+          //
+          int c (e.code ().value ());
+          if (!(e.code ().category () == generic_category () &&
+                (c == ENOSYS || // Not implemented.
+                 c == EPERM)))  // Not supported by the filesystem(s).
+            fail () << "unable to create symlink '" << link << "' to '"
+                    << target << "': " << e;
+
+          try
+          {
+            mkhardlink (target, link, dir);
+
+            if (cleanup)
+              sp.clean ({cleanup_type::always, link}, true);
+          }
+          catch (const system_error& e)
+          {
+            c = e.code ().value ();
+            if (!(e.code ().category () == generic_category () &&
+                  (c == ENOSYS || // Not implemented.
+                   c == EPERM  || // Not supported by the filesystem(s).
+                   c == EXDEV)))  // On different filesystems.
+              fail () << "unable to create hardlink '" << link << "' to '"
+                      << target << "': " << e;
+
+            if (dir)
+              cpdir (sp,
+                     path_cast<dir_path> (target), path_cast<dir_path> (link),
+                     false,
+                     cleanup,
+                     fail);
+            else
+              cpfile (sp,
+                      target,
+                      link,
+                      false /* overwrite */,
+                      true /* attrs */,
+                      cleanup,
+                      fail);
+          }
+        }
+      }
+
+      // ln [--no-cleanup] -s <target-path>    <link-path>
+      // ln [--no-cleanup] -s <target-path>... <link-dir>/
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      ln (scope& sp,
+          const strings& args,
+          auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "ln");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool cleanup (true);
+          bool symlink (false);
+
+          for (; i != e; ++i)
+          {
+            const string& o (*i);
+
+            if (o == "--no-cleanup")
+              cleanup = false;
+            else if (o == "-s")
+              symlink = true;
+            else
+            {
+              if (o == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          if (!symlink)
+            error () << "missing -s option";
+
+          // Create file or directory symlinks.
+          //
+          if (i == e)
+            error () << "missing arguments";
+
+          const dir_path& wd (sp.wd_path);
+
+          auto j (args.rbegin ());
+          path link (parse_path (*j++, wd));
+          e = j.base ();
+
+          if (i == e)
+            error () << "missing target path";
+
+          auto fail = [&error] () {return error (true);};
+
+          // If link is not a directory path (no trailing separator), then
+          // create a symlink to the target path at the specified link path
+          // (the only target path is allowed in such a case). Otherwise create
+          // links to the target paths inside the specified directory.
+          //
+          if (!link.to_directory ())
+          {
+            path target (parse_path (*i++, wd));
+
+            // If there are multiple targets but no trailing separator for the
+            // link, then, most likelly, it is missing.
+            //
+            if (i != e)
+              error () << "multiple target paths with non-directory link path";
+
+            // Synopsis 1: create a target path symlink at the specified path.
+            //
+            mksymlink (sp, target, link, cleanup, fail);
+          }
+          else
+          {
+            for (; i != e; ++i)
+            {
+              path target (parse_path (*i, wd));
+
+              // Synopsis 2: create a target path symlink in the specified
+              // directory.
+              //
+              mksymlink (sp, target, link / target.leaf (), cleanup, fail);
+            }
+          }
+
+          r = 0;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // Create a directory if not exist and its parent directories if
+      // necessary. Throw system_error on failure. Register created
+      // directories for cleanup. The directory path must be absolute.
+      //
+      static void
+      mkdir_p (scope& sp, const dir_path& p, bool cleanup)
+      {
+        if (!dir_exists (p))
+        {
+          if (!p.root ())
+            mkdir_p (sp, p.directory (), cleanup);
+
+          try_mkdir (p); // Returns success or throws.
+
+          if (cleanup)
+            sp.clean ({cleanup_type::always, p}, true);
+        }
+      }
+
+      // mkdir [--no-cleanup] [-p] <dir>...
+      //
+      // Note that POSIX doesn't specify if after a directory creation failure
+      // the command should proceed with the rest of the arguments. The current
+      // implementation exits immediatelly in such a case.
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      mkdir (scope& sp,
+             const strings& args,
+             auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "mkdir");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool parent (false);
+          bool cleanup (true);
+          for (; i != e; ++i)
+          {
+            const string& o (*i);
+
+            if (o == "-p")
+              parent = true;
+            else if (o == "--no-cleanup")
+              cleanup = false;
+            else
+            {
+              if (*i == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          // Create directories.
+          //
+          if (i == e)
+            error () << "missing directory";
+
+          for (; i != e; ++i)
+          {
+            dir_path p (path_cast<dir_path> (parse_path (*i, sp.wd_path)));
+
+            try
+            {
+              if (parent)
+                mkdir_p (sp, p, cleanup);
+              else if (try_mkdir (p) == mkdir_status::success)
+              {
+                if (cleanup)
+                  sp.clean ({cleanup_type::always, p}, true);
+              }
+              else //                == mkdir_status::already_exists
+                throw_generic_error (EEXIST);
+            }
+            catch (const system_error& e)
+            {
+              error () << "unable to create directory '" << p << "': " << e;
+            }
+          }
+
+          r = 0;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // mv [--no-cleanup] [-f] <src-path>    <dst-path>
+      // mv [--no-cleanup] [-f] <src-path>... <dst-dir>/
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      mv (scope& sp,
+          const strings& args,
+          auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "mv");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool no_cleanup (false);
+          bool force (false);
+          for (; i != e; ++i)
+          {
+            const string& o (*i);
+
+            if (o == "--no-cleanup")
+              no_cleanup = true;
+            else if (*i == "-f")
+              force = true;
+            else
+            {
+              if (o == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          // Move filesystem entries.
+          //
+          if (i == e)
+            error () << "missing arguments";
+
+          const dir_path& wd (sp.wd_path);
+
+          auto j (args.rbegin ());
+          path dst (parse_path (*j++, wd));
+          e = j.base ();
+
+          if (i == e)
+            error () << "missing source path";
+
+          auto mv = [no_cleanup, force, &wd, &sp, &error] (const path& from,
+                                                           const path& to)
+          {
+            const dir_path& rwd (sp.root->wd_path);
+
+            if (!from.sub (rwd) && !force)
+              error () << "'" << from << "' is out of working directory '"
+                       << rwd << "'";
+
+            try
+            {
+              auto check_wd = [&wd, &error] (const path& p)
+              {
+                if (wd.sub (path_cast<dir_path> (p)))
+                  error () << "'" << p << "' contains test working directory '"
+                           << wd << "'";
+              };
+
+              check_wd (from);
+              check_wd (to);
+
+              bool exists (butl::entry_exists (to));
+
+              // Fail if the source and destination paths are the same.
+              //
+              // Note that for mventry() function (that is based on the POSIX
+              // rename() function) this is a noop.
+              //
+              if (exists && to == from)
+                error () << "unable to move entity '" << from << "' to itself";
+
+              // Rename/move the filesystem entry, replacing an existing one.
+              //
+              mventry (from,
+                       to,
+                       cpflags::overwrite_permissions |
+                       cpflags::overwrite_content);
+
+              // Unless suppressed, adjust the cleanups that are sub-paths of
+              // the source path.
+              //
+              if (!no_cleanup)
+              {
+                // "Move" the matching cleanup if the destination path doesn't
+                // exist and is a sub-path of the working directory. Otherwise
+                // just remove it.
+                //
+                // Note that it's not enough to just change the cleanup paths.
+                // We also need to make sure that these cleanups happen before
+                // the destination directory (or any of its parents) cleanup,
+                // that is potentially registered. To achieve that we can just
+                // relocate these cleanup entries to the end of the list,
+                // preserving their mutual order. Remember that cleanups in
+                // the list are executed in the reversed order.
+                //
+                bool mv_cleanups (!exists && to.sub (rwd));
+                cleanups cs;
+
+                // Remove the source path sub-path cleanups from the list,
+                // adjusting/caching them if required (see above).
+                //
+                for (auto i (sp.cleanups.begin ()); i != sp.cleanups.end (); )
+                {
+                  cleanup& c (*i);
+                  path&    p (c.path);
+
+                  if (p.sub (from))
+                  {
+                    if (mv_cleanups)
+                    {
+                      // Note that we need to preserve the cleanup path
+                      // trailing separator which indicates the removal
+                      // method. Also note that leaf(), in particular, does
+                      // that.
+                      //
+                      p = p != from
+                        ? to / p.leaf (path_cast<dir_path> (from))
+                        : p.to_directory ()
+                          ? path_cast<dir_path> (to)
+                          : to;
+
+                      cs.push_back (move (c));
+                    }
+
+                    i = sp.cleanups.erase (i);
+                  }
+                  else
+                    ++i;
+                }
+
+                // Re-insert the adjusted cleanups at the end of the list.
+                //
+                sp.cleanups.insert (sp.cleanups.end (),
+                                    make_move_iterator (cs.begin ()),
+                                    make_move_iterator (cs.end ()));
+              }
+            }
+            catch (const system_error& e)
+            {
+              error () << "unable to move entity '" << from << "' to '" << to
+                       << "': " << e;
+            }
+          };
+
+          // If destination is not a directory path (no trailing separator)
+          // then move the filesystem entry to the specified path (the only
+          // source path is allowed in such a case). Otherwise move the source
+          // filesystem entries into the destination directory.
+          //
+          if (!dst.to_directory ())
+          {
+            path src (parse_path (*i++, wd));
+
+            // If there are multiple sources but no trailing separator for the
+            // destination, then, most likelly, it is missing.
+            //
+            if (i != e)
+              error () << "multiple source paths without trailing separator "
+                       << "for destination directory";
+
+            // Synopsis 1: move an entity to the specified path.
+            //
+            mv (src, dst);
+          }
+          else
+          {
+            // Synopsis 2: move entities into the specified directory.
+            //
+            for (; i != e; ++i)
+            {
+              path src (parse_path (*i, wd));
+              mv (src, dst / src.leaf ());
+            }
+          }
+
+          r = 0;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // rm [-r] [-f] <path>...
+      //
+      // The implementation deviates from POSIX in a number of ways. It doesn't
+      // interact with a user and fails immediatelly if unable to process an
+      // argument. It doesn't check for dots containment in the path, and
+      // doesn't consider files and directory permissions in any way just
+      // trying to remove a filesystem entry. Always fails if empty path is
+      // specified.
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      rm (scope& sp,
+          const strings& args,
+          auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "rm");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool dir (false);
+          bool force (false);
+          for (; i != e; ++i)
+          {
+            if (*i == "-r")
+              dir = true;
+            else if (*i == "-f")
+              force = true;
+            else
+            {
+              if (*i == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          // Remove entries.
+          //
+          if (i == e && !force)
+            error () << "missing file";
+
+          const dir_path& wd  (sp.wd_path);
+          const dir_path& rwd (sp.root->wd_path);
+
+          for (; i != e; ++i)
+          {
+            path p (parse_path (*i, wd));
+
+            if (!p.sub (rwd) && !force)
+              error () << "'" << p << "' is out of working directory '" << rwd
+                       << "'";
+
+            try
+            {
+              dir_path d (path_cast<dir_path> (p));
+
+              if (dir_exists (d))
+              {
+                if (!dir)
+                  error () << "'" << p << "' is a directory";
+
+                if (wd.sub (d))
+                  error () << "'" << p << "' contains test working directory '"
+                           << wd << "'";
+
+                // The call can result in rmdir_status::not_exist. That's not
+                // very likelly but there is also nothing bad about it.
+                //
+                try_rmdir_r (d);
+              }
+              else if (try_rmfile (p) == rmfile_status::not_exist && !force)
+                throw_generic_error (ENOENT);
+            }
+            catch (const system_error& e)
+            {
+              error () << "unable to remove '" << p << "': " << e;
+            }
+          }
+
+          r = 0;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // rmdir [-f] <path>...
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      rmdir (scope& sp,
+             const strings& args,
+             auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "rmdir");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool force (false);
+          for (; i != e; ++i)
+          {
+            if (*i == "-f")
+              force = true;
+            else
+            {
+              if (*i == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          // Remove directories.
+          //
+          if (i == e && !force)
+            error () << "missing directory";
+
+          const dir_path& wd  (sp.wd_path);
+          const dir_path& rwd (sp.root->wd_path);
+
+          for (; i != e; ++i)
+          {
+            dir_path p (path_cast<dir_path> (parse_path (*i, wd)));
+
+            if (wd.sub (p))
+              error () << "'" << p << "' contains test working directory '"
+                       << wd << "'";
+
+            if (!p.sub (rwd) && !force)
+              error () << "'" << p << "' is out of working directory '"
+                       << rwd << "'";
+
+            try
+            {
+              rmdir_status s (try_rmdir (p));
+
+              if (s == rmdir_status::not_empty)
+                throw_generic_error (ENOTEMPTY);
+              else if (s == rmdir_status::not_exist && !force)
+                throw_generic_error (ENOENT);
+            }
+            catch (const system_error& e)
+            {
+              error () << "unable to remove '" << p << "': " << e;
+            }
+          }
+
+          r = 0;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // sed [-n] [-i] -e <script> [<file>]
+      //
+      // Note: must be executed asynchronously.
+      //
+      static uint8_t
+      sed (scope& sp,
+           const strings& args,
+           auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "sed");
+        };
+
+        try
+        {
+          // Automatically remove a temporary file (used for in place editing)
+          // on failure.
+          //
+          auto_rmfile rm;
+
+          // Do not throw when failbit is set (getline() failed to extract any
+          // character).
+          //
+          ifdstream cin  (move (in), ifdstream::badbit);
+          ofdstream cout (move (out));
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool auto_prn (true);
+          bool in_place (false);
+
+          struct substitute
+          {
+            string regex;
+            string replacement;
+            bool icase  = false;
+            bool global = false;
+            bool print  = false;
+          };
+          optional<substitute> subst;
+
+          for (; i != e; ++i)
+          {
+            const string& o (*i);
+
+            if (o == "-n")
+              auto_prn = false;
+            else if (o == "-i")
+              in_place = true;
+            else if (o == "-e")
+            {
+              // Only a single script is supported.
+              //
+              if (subst)
+                error () << "multiple scripts";
+
+              // If option has no value then bail out and report.
+              //
+              if (++i == e)
+                break;
+
+              const string& v (*i);
+              if (v.empty ())
+                error () << "empty script";
+
+              if (v[0] != 's')
+                error () << "only 's' command supported";
+
+              // Parse the substitute command.
+              //
+              if (v.size () < 2)
+                error () << "no delimiter for 's' command";
+
+              char delim (v[1]);
+              if (delim == '\\' || delim == '\n')
+                error () << "invalid delimiter for 's' command";
+
+              size_t p (v.find (delim, 2));
+              if (p == string::npos)
+                error () << "unterminated 's' command regex";
+
+              subst = substitute ();
+              subst->regex.assign (v, 2, p - 2);
+
+              // Empty regex matches nothing, so not of much use.
+              //
+              if (subst->regex.empty ())
+                error () << "empty regex in 's' command";
+
+              size_t b (p + 1);
+              p = v.find (delim, b);
+              if (p == string::npos)
+                error () << "unterminated 's' command replacement";
+
+              subst->replacement.assign (v, b, p - b);
+
+              // Parse the substitute command flags.
+              //
+              char c;
+              for (++p; (c = v[p]) != '\0'; ++p)
+              {
+                switch (c)
+                {
+                case 'i': subst->icase  = true; break;
+                case 'g': subst->global = true; break;
+                case 'p': subst->print  = true; break;
+                default:
+                  {
+                    error () << "invalid 's' command flag '" << c << "'";
+                  }
+                }
+              }
+            }
+            else
+            {
+              if (o == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          if (!subst)
+            error () << "missing script";
+
+          // Path of a file to edit. An empty path represents stdin.
+          //
+          path p;
+          if (i != e)
+          {
+            if (*i != "-")
+              p = parse_path (*i, sp.wd_path);
+
+            ++i;
+          }
+
+          if (i != e)
+            error () << "unexpected argument '" << *i << "'";
+
+          // If we edit file in place make sure that the file path is specified
+          // and obtain a temporary file path. We will be writing to the
+          // temporary file (rather than to stdout) and will move it to the
+          // original file path afterwards.
+          //
+          path tp;
+          if (in_place)
+          {
+            if (p.empty ())
+              error () << "-i option specified while reading from stdin";
+
+            try
+            {
+              tp = path::temp_path ("build2-sed");
+
+              cout.close ();  // Flush and close.
+
+              cout.open (
+                fdopen (tp,
+                        fdopen_mode::out | fdopen_mode::truncate |
+                        fdopen_mode::create,
+                        path_permissions (p)));
+            }
+            catch (const io_error& e)
+            {
+              error_record d (error ());
+              d << "unable to open '" << tp << "': " << e;
+            }
+            catch (const system_error& e)
+            {
+              error_record d (error ());
+              d << "unable to obtain temporary file: " << e;
+            }
+
+            rm = auto_rmfile (tp);
+          }
+
+          // Note that ECMAScript is implied if no grammar flag is specified.
+          //
+          regex re (subst->regex,
+                    subst->icase ? regex::icase : regex::ECMAScript);
+
+          // Edit a file or STDIN.
+          //
+          try
+          {
+            // Open a file if specified.
+            //
+            if (!p.empty ())
+            {
+              cin.close (); // Flush and close.
+              cin.open (p);
+            }
+
+            // Read until failbit is set (throw on badbit).
+            //
+            string s;
+            while (getline (cin, s))
+            {
+              auto r (regex_replace_search (
+                        s,
+                        re,
+                        subst->replacement,
+                        subst->global
+                        ? regex_constants::format_default
+                        : regex_constants::format_first_only));
+
+              // Add newline regardless whether the source line is newline-
+              // terminated or not (in accordance with POSIX).
+              //
+              if (auto_prn || (r.second && subst->print))
+                cout << r.first << '\n';
+            }
+
+            cin.close ();
+            cout.close ();
+
+            if (in_place)
+            {
+              mvfile (
+                tp, p,
+                cpflags::overwrite_content | cpflags::overwrite_permissions);
+
+              rm.cancel ();
+            }
+
+            r = 0;
+          }
+          catch (const io_error& e)
+          {
+            error_record d (error ());
+            d << "unable to edit ";
+
+            if (p.empty ())
+              d << "stdin";
+            else
+              d << "'" << p << "'";
+
+            d << ": " << e;
+          }
+        }
+        catch (const regex_error& e)
+        {
+          // Print regex_error description if meaningful (no space).
+          //
+          error (false) << "invalid regex" << e;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while creating cin, cout or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const system_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // sleep <seconds>
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      sleep (scope&,
+             const strings& args,
+             auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "sleep");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          if (args.empty ())
+            error () << "missing time interval";
+
+          if (args.size () > 1)
+            error () << "unexpected argument '" << args[1] << "'";
+
+          uint64_t n;
+
+          for (;;) // Breakout loop.
+          {
+            const string& a (args[0]);
+
+            // Note: strtoull() allows these.
+            //
+            if (!a.empty () && a[0] != '-' && a[0] != '+')
+            {
+              char* e (nullptr);
+              n = strtoull (a.c_str (), &e, 10); // Can't throw.
+
+              if (errno != ERANGE && e == a.c_str () + a.size ())
+                break;
+            }
+
+            error () << "invalid time interval '" << a << "'";
+          }
+
+          // If/when required we could probably support the precise sleep mode
+          // (e.g., via an option).
+          //
+          sched.sleep (chrono::seconds (n));
+
+          r = 0;
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // test -f|-d <path>
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      test (scope& sp,
+            const strings& args,
+            auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (2);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "test");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          if (args.size () < 2)
+            error () << "missing path";
+
+          bool file (args[0] == "-f");
+
+          if (!file && args[0] != "-d")
+            error () << "invalid option";
+
+          if (args.size () > 2)
+            error () << "unexpected argument '" << args[2] << "'";
+
+          path p (parse_path (args[1], sp.wd_path));
+
+          try
+          {
+            r = (file ? file_exists (p) : dir_exists (p)) ? 0 : 1;
+          }
+          catch (const system_error& e)
+          {
+            error () << "cannot test '" << p << "': " << e;
+          }
+        }
+        catch (const invalid_path& e)
+        {
+          error (false)  << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 2;
+      }
+
+      // touch [--no-cleanup] [--after <ref-file>] <file>...
+      //
+      // Note that POSIX doesn't specify the behavior for touching an entry
+      // other than file.
+      //
+      // Also note that POSIX doesn't specify if after a file touch failure the
+      // command should proceed with the rest of the arguments. The current
+      // implementation exits immediatelly in such a case.
+      //
+      // Note: can be executed synchronously.
+      //
+      static uint8_t
+      touch (scope& sp,
+             const strings& args,
+             auto_fd in, auto_fd out, auto_fd err) noexcept
+      try
+      {
+        uint8_t r (1);
+        ofdstream cerr (move (err));
+
+        auto error = [&cerr] (bool fail = true)
+        {
+          return error_record (cerr, fail, "touch");
+        };
+
+        try
+        {
+          in.close ();
+          out.close ();
+
+          auto mtime = [&error] (const path& p) -> timestamp
+          {
+            try
+            {
+              timestamp t (file_mtime (p));
+
+              if (t == timestamp_nonexistent)
+                throw_generic_error (ENOENT);
+
+              return t;
+            }
+            catch (const system_error& e)
+            {
+              error () << "cannot obtain file '" << p
+                       << "' modification time: " << e;
+            }
+            assert (false); // Can't be here.
+            return timestamp ();
+          };
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool cleanup (true);
+          optional<timestamp> after;
+          for (; i != e; ++i)
+          {
+            const string& o (*i);
+
+            if (o == "--no-cleanup")
+              cleanup = false;
+            else if (o == "--after")
+            {
+              if (++i == e)
+                error () << "missing --after option value";
+
+              after = mtime (parse_path (*i, sp.wd_path));
+            }
+            else
+            {
+              if (o == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          if (i == e)
+            error () << "missing file";
+
+          // Create files.
+          //
+          for (; i != e; ++i)
+          {
+            path p (parse_path (*i, sp.wd_path));
+
+            try
+            {
+              // Note that we don't register (implicit) cleanup for an
+              // existing path.
+              //
+              if (touch_file (p) && cleanup)
+                sp.clean ({cleanup_type::always, p}, true);
+
+              if (after)
+              {
+                while (mtime (p) <= *after)
+                  touch_file (p, false /* create */);
+              }
+            }
+            catch (const system_error& e)
+            {
+              error () << "cannot create/update '" << p << "': " << e;
+            }
+          }
+
+          r = 0;
+        }
+        catch (const invalid_path& e)
+        {
+          error (false) << "invalid path '" << e.path << "'";
+        }
+        // Can be thrown while closing in, out or writing to cerr.
+        //
+        catch (const io_error& e)
+        {
+          error (false) << e;
+        }
+        catch (const failed&)
+        {
+          // Diagnostics has already been issued.
+        }
+
+        cerr.close ();
+        return r;
+      }
+      catch (const std::exception&)
+      {
+        return 1;
+      }
+
+      // Run builtin implementation asynchronously.
+      //
+      static builtin
+      async_impl (builtin_impl* fn,
+                  scope& sp,
+                  uint8_t& r,
+                  const strings& args,
+                  auto_fd in, auto_fd out, auto_fd err)
+      {
+        return builtin (
+          r,
+          thread ([fn, &sp, &r, &args,
+                   in  = move (in),
+                   out = move (out),
+                   err = move (err)] () mutable noexcept
+                  {
+                    r = fn (sp, args, move (in), move (out), move (err));
+                  }));
+      }
+
+      template <builtin_impl fn>
+      static builtin
+      async_impl (scope& sp,
+                  uint8_t& r,
+                  const strings& args,
+                  auto_fd in, auto_fd out, auto_fd err)
+      {
+        return async_impl (fn, sp, r, args, move (in), move (out), move (err));
+      }
+
+      // Run builtin implementation synchronously.
+      //
+      template <builtin_impl fn>
+      static builtin
+      sync_impl (scope& sp,
+                 uint8_t& r,
+                 const strings& args,
+                 auto_fd in, auto_fd out, auto_fd err)
+      {
+        r = fn (sp, args, move (in), move (out), move (err));
+        return builtin (r, thread ());
+      }
+
+      const builtin_map builtins
+      {
+        {"cat",   &async_impl<&cat>},
+        {"cp",    &sync_impl<&cp>},
+        {"echo",  &async_impl<&echo>},
+        {"false", &false_},
+        {"ln",    &sync_impl<&ln>},
+        {"mkdir", &sync_impl<&mkdir>},
+        {"mv",    &sync_impl<&mv>},
+        {"rm",    &sync_impl<&rm>},
+        {"rmdir", &sync_impl<&rmdir>},
+        {"sed",   &async_impl<&sed>},
+        {"sleep", &sync_impl<&sleep>},
+        {"test",  &sync_impl<&test>},
+        {"touch", &sync_impl<&touch>},
+        {"true",  &true_}
+      };
+    }
+  }
+}
diff --git a/libbuild2/test/script/builtin.hxx b/libbuild2/test/script/builtin.hxx
new file mode 100644
index 0000000..b340335
--- /dev/null
+++ b/libbuild2/test/script/builtin.hxx
@@ -0,0 +1,74 @@
+// file      : libbuild2/test/script/builtin.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_TEST_SCRIPT_BUILTIN_HXX
+#define LIBBUILD2_TEST_SCRIPT_BUILTIN_HXX
+
+#include <map>
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      class scope;
+
+      // A process/thread-like object representing a running builtin.
+      //
+      // For now, instead of allocating the result storage dynamically, we
+      // expect it to be provided by the caller.
+      //
+      class builtin
+      {
+      public:
+        uint8_t
+        wait () {if (t_.joinable ()) t_.join (); return r_;}
+
+        ~builtin () {wait ();}
+
+      public:
+        builtin (uint8_t& r, thread&& t = thread ()): r_ (r), t_ (move (t)) {}
+
+        builtin (builtin&&) = default;
+
+      private:
+        uint8_t& r_;
+        thread t_;
+      };
+
+      // Start builtin command. Throw system_error on failure.
+      //
+      // Note that unlike argc/argv, our args don't include the program name.
+      //
+      using builtin_func = builtin (scope&,
+                                    uint8_t& result,
+                                    const strings& args,
+                                    auto_fd in, auto_fd out, auto_fd err);
+
+      class builtin_map: public std::map<string, builtin_func*>
+      {
+      public:
+        using base = std::map<string, builtin_func*>;
+        using base::base;
+
+        // Return NULL if not a builtin.
+        //
+        builtin_func*
+        find (const string& n) const
+        {
+          auto i (base::find (n));
+          return i != end () ? i->second : nullptr;
+        }
+      };
+
+      extern const builtin_map builtins;
+    }
+  }
+}
+
+#endif // LIBBUILD2_TEST_SCRIPT_BUILTIN_HXX
diff --git a/libbuild2/test/script/lexer+command-expansion.test.testscript b/libbuild2/test/script/lexer+command-expansion.test.testscript
new file mode 100644
index 0000000..1ddc246
--- /dev/null
+++ b/libbuild2/test/script/lexer+command-expansion.test.testscript
@@ -0,0 +1,248 @@
+# file      : libbuild2/test/script/lexer+command-expansion.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+test.arguments = command-expansion
+
+: pass-redirect
+:
+{
+  : in
+  :
+  $* <:"0<|" >>EOO
+  '0'
+  <|
+  EOO
+
+  : arg-in
+  :
+  $* <:"0 <|" >>EOO
+  '0 '
+  <|
+  EOO
+
+  : out
+  :
+  $* <:"1>|" >>EOO
+  '1'
+  >|
+  EOO
+
+  : arg-out
+  :
+  $* <:"1 >|" >>EOO
+  '1 '
+  >|
+  EOO
+}
+
+: null-redirect
+:
+{
+  : in
+  :
+  $* <:"0<-" >>EOO
+  '0'
+  <-
+  EOO
+
+  : arg-in
+  :
+  $* <:"0 <-" >>EOO
+  '0 '
+  <-
+  EOO
+
+  : out
+  :
+  $* <:"1>-" >>EOO
+  '1'
+  >-
+  EOO
+
+  : arg-out
+  :
+  $* <:"1 >-" >>EOO
+  '1 '
+  >-
+  EOO
+}
+
+: trace-redirect
+:
+{
+  : out
+  :
+  $* <:"1>!" >>EOO
+  '1'
+  >!
+  EOO
+
+  : arg-out
+  :
+  $* <:"1 >!" >>EOO
+  '1 '
+  >!
+  EOO
+}
+
+: merge-redirect
+:
+{
+  : out
+  :
+  $* <:"1>&2" >>EOO
+  '1'
+  >&
+  '2'
+  EOO
+
+  : arg-out
+  :
+  $* <:"1 >&2" >>EOO
+  '1 '
+  >&
+  '2'
+  EOO
+}
+
+: str-redirect
+:
+{
+  : in
+  :
+  {
+    : newline
+    :
+    $* <:"0<a b" >>EOO
+    '0'
+    <
+    'a b'
+    EOO
+
+    : no-newline
+    :
+    $* <:"0<:a b" >>EOO
+    '0'
+    <:
+    'a b'
+    EOO
+  }
+
+  : out
+  :
+  {
+    : newline
+    :
+    $* <:"1>a b" >>EOO
+    '1'
+    >
+    'a b'
+    EOO
+
+    : no-newline
+    :
+    $* <:"1>:a b" >>EOO
+    '1'
+    >:
+    'a b'
+    EOO
+  }
+}
+
+: doc-redirect
+:
+{
+  : in
+  :
+  {
+    : newline
+    :
+    $* <:"0<<E O I" >>EOO
+    '0'
+    <<
+    'E O I'
+    EOO
+
+    : no-newline
+    :
+    $* <:"0<<:E O I" >>EOO
+    '0'
+    <<:
+    'E O I'
+    EOO
+  }
+
+  : out
+  :
+  {
+    : newline
+    :
+    $* <:"1>>E O O" >>EOO
+    '1'
+    >>
+    'E O O'
+    EOO
+
+    : no-newline
+    :
+    $* <:"1>>:E O O" >>EOO
+    '1'
+    >>:
+    'E O O'
+    EOO
+  }
+}
+
+: file-redirect
+:
+{
+  : in
+  :
+  $* <:"0<<<a b" >>EOO
+  '0'
+  <<<
+  'a b'
+  EOO
+
+  : out
+  :
+  $* <:"1>=a b" >>EOO
+  '1'
+  >=
+  'a b'
+  EOO
+
+  : out-app
+  :
+  $* <:"1>+a b" >>EOO
+  '1'
+  >+
+  'a b'
+  EOO
+}
+
+: cleanup
+:
+{
+  : always
+  :
+  $* <:"&file" >>EOO
+  &
+  'file'
+  EOO
+
+  : maybe
+  :
+  $* <:"&?file" >>EOO
+  &?
+  'file'
+  EOO
+
+  : never
+  :
+  $* <:"&!file" >>EOO
+  &!
+  'file'
+  EOO
+}
diff --git a/libbuild2/test/script/lexer+command-line.test.testscript b/libbuild2/test/script/lexer+command-line.test.testscript
new file mode 100644
index 0000000..eedb46f
--- /dev/null
+++ b/libbuild2/test/script/lexer+command-line.test.testscript
@@ -0,0 +1,208 @@
+# file      : libbuild2/test/script/lexer+command-line.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+test.arguments = command-line
+
+: semi
+{
+  : immediate
+  :
+  $* <"cmd;" >>EOO
+  'cmd'
+  ;
+  <newline>
+  EOO
+
+  : separated
+  :
+  $* <"cmd ;" >>EOO
+  'cmd'
+  ;
+  <newline>
+  EOO
+
+  : only
+  :
+  $* <";" >>EOO
+  ;
+  <newline>
+  EOO
+}
+
+: colon
+:
+{
+  : immediate
+  :
+  $* <"cmd: dsc" >>EOO
+  'cmd'
+  :
+  'dsc'
+  <newline>
+  EOO
+
+  : separated
+  :
+  $* <"cmd :dsc" >>EOO
+  'cmd'
+  :
+  'dsc'
+  <newline>
+  EOO
+
+  : only
+  :
+  $* <":" >>EOO
+  :
+  <newline>
+  EOO
+}
+
+: redirect
+:
+{
+  : pass
+  :
+  $* <"cmd <| 1>|" >>EOO
+  'cmd'
+  <|
+  '1'
+  >|
+  <newline>
+  EOO
+
+  : null
+  :
+  $* <"cmd <- 1>-" >>EOO
+  'cmd'
+  <-
+  '1'
+  >-
+  <newline>
+  EOO
+
+  : trace
+  :
+  $* <"cmd 1>!" >>EOO
+  'cmd'
+  '1'
+  >!
+  <newline>
+  EOO
+
+  : merge
+  :
+  $* <"cmd 1>&2" >>EOO
+  'cmd'
+  '1'
+  >&
+  '2'
+  <newline>
+  EOO
+
+  : str
+  :
+  $* <"cmd <a 1>b" >>EOO
+  'cmd'
+  <
+  'a'
+  '1'
+  >
+  'b'
+  <newline>
+  EOO
+
+  : str-nn
+  :
+  $* <"cmd <:a 1>:b" >>EOO
+  'cmd'
+  <:
+  'a'
+  '1'
+  >:
+  'b'
+  <newline>
+  EOO
+
+  : doc
+  :
+  $* <"cmd <<EOI 1>>EOO" >>EOO
+  'cmd'
+  <<
+  'EOI'
+  '1'
+  >>
+  'EOO'
+  <newline>
+  EOO
+
+  : doc-nn
+  :
+  $* <"cmd <<:EOI 1>>:EOO" >>EOO
+  'cmd'
+  <<:
+  'EOI'
+  '1'
+  >>:
+  'EOO'
+  <newline>
+  EOO
+
+  : file-cmp
+  :
+  $* <"cmd <<<in >>>out 2>>>err" >>EOO
+  'cmd'
+  <<<
+  'in'
+  >>>
+  'out'
+  '2'
+  >>>
+  'err'
+  <newline>
+  EOO
+
+  : file-write
+  :
+  $* <"cmd >=out 2>+err" >>EOO
+  'cmd'
+  >=
+  'out'
+  '2'
+  >+
+  'err'
+  <newline>
+  EOO
+}
+
+: cleanup
+:
+{
+  : always
+  :
+  $* <"cmd &file" >>EOO
+  'cmd'
+  &
+  'file'
+  <newline>
+  EOO
+
+  : maybe
+  :
+  $* <"cmd &?file" >>EOO
+  'cmd'
+  &?
+  'file'
+  <newline>
+  EOO
+
+  : never
+  :
+  $* <"cmd &!file" >>EOO
+  'cmd'
+  &!
+  'file'
+  <newline>
+  EOO
+}
diff --git a/libbuild2/test/script/lexer+description-line.test.testscript b/libbuild2/test/script/lexer+description-line.test.testscript
new file mode 100644
index 0000000..bb5948a
--- /dev/null
+++ b/libbuild2/test/script/lexer+description-line.test.testscript
@@ -0,0 +1,33 @@
+# file      : libbuild2/test/script/lexer+description-line.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+test.arguments = description-line
+
+: full
+:
+$* <" foo  bar " >>EOO
+' foo  bar '
+<newline>
+EOO
+
+: space
+:
+$* <"  " >>EOO
+'  '
+<newline>
+EOO
+
+: empty
+:
+$* <"" >>EOO
+<newline>
+EOO
+
+: eof
+:
+$* <:"foo" >>EOO 2>>EOE != 0
+'foo'
+EOO
+stdin:1:4: error: expected newline at the end of description line
+EOE
diff --git a/libbuild2/test/script/lexer+first-token.test.testscript b/libbuild2/test/script/lexer+first-token.test.testscript
new file mode 100644
index 0000000..3eaf976
--- /dev/null
+++ b/libbuild2/test/script/lexer+first-token.test.testscript
@@ -0,0 +1,97 @@
+# file      : libbuild2/test/script/lexer+first-token.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+# Note: this mode auto-expires after each token.
+#
+test.arguments = first-token
+
+: dot
+:
+$* <"." >>EOO
+.
+<newline>
+EOO
+
+: semi
+:
+$* <";" >>EOO
+;
+<newline>
+EOO
+
+: colon
+:
+$* <":" >>EOO
+:
+<newline>
+EOO
+
+: lcbrace
+:
+$* <"{" >>EOO
+{
+<newline>
+EOO
+
+: rcbrace
+:
+$* <"}" >>EOO
+}
+<newline>
+EOO
+
+: setup
+:
+$* <"+foo" >>EOO
++
+'foo'
+<newline>
+EOO
+
+: tdown
+:
+$* <"- foo" >>EOO
+-
+'foo'
+<newline>
+EOO
+
+: plus-leading
+:
+$* <"foo+bar" >>EOO
+'foo+bar'
+<newline>
+EOO
+
+: minus-leading
+:
+$* <"foo- x" >>EOO
+'foo-'
+'x'
+<newline>
+EOO
+
+: assign
+:
+$* <"foo=" >>EOO
+'foo'
+'='
+<newline>
+EOO
+
+: append
+:
+$* <"foo+=" >>EOO
+'foo'
+'+='
+<newline>
+EOO
+
+: prepend
+:
+$* <"foo=+" >>EOO
+'foo'
+'=+'
+<newline>
+EOO
diff --git a/libbuild2/test/script/lexer+second-token.test.testscript b/libbuild2/test/script/lexer+second-token.test.testscript
new file mode 100644
index 0000000..c494796
--- /dev/null
+++ b/libbuild2/test/script/lexer+second-token.test.testscript
@@ -0,0 +1,68 @@
+# file      : libbuild2/test/script/lexer+second-token.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+# Note: this mode auto-expires after each token.
+#
+test.arguments = second-token
+
+: semi
+:
+$* <";" >>EOO
+;
+<newline>
+EOO
+
+: colon
+:
+$* <":" >>EOO
+:
+<newline>
+EOO
+
+: assign
+:
+$* <"=foo" >>EOO
+=
+'foo'
+<newline>
+EOO
+
+: append
+:
+$* <"+= foo" >>EOO
++=
+'foo'
+<newline>
+EOO
+
+: prepend
+:
+$* <" =+ foo" >>EOO
+=+
+'foo'
+<newline>
+EOO
+
+: assign-leading
+:
+$* <"foo=bar" >>EOO
+'foo=bar'
+<newline>
+EOO
+
+: append-leading
+:
+$* <"foo+= bar" >>EOO
+'foo+='
+'bar'
+<newline>
+EOO
+
+: prepend-leading
+:
+$* <"foo =+bar" >>EOO
+'foo'
+'=+bar'
+<newline>
+EOO
diff --git a/libbuild2/test/script/lexer+variable-line.test.testscript b/libbuild2/test/script/lexer+variable-line.test.testscript
new file mode 100644
index 0000000..bac4f16
--- /dev/null
+++ b/libbuild2/test/script/lexer+variable-line.test.testscript
@@ -0,0 +1,28 @@
+# file      : libbuild2/test/script/lexer+variable-line.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+test.arguments = variable-line
+
+: semi
+:
+$* <"cmd;" >>EOO
+'cmd'
+;
+<newline>
+EOO
+
+: semi-separated
+:
+$* <"cmd ;" >>EOO
+'cmd'
+;
+<newline>
+EOO
+
+: semi-only
+:
+$* <";" >>EOO
+;
+<newline>
+EOO
diff --git a/libbuild2/test/script/lexer+variable.test.testscript b/libbuild2/test/script/lexer+variable.test.testscript
new file mode 100644
index 0000000..64b2bee
--- /dev/null
+++ b/libbuild2/test/script/lexer+variable.test.testscript
@@ -0,0 +1,70 @@
+# file      : libbuild2/test/script/lexer+variable.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+# Test handling custom variable names ($*, $~, $NN).
+#
+test.arguments = variable
+
+: command
+:
+{
+  : only
+  :
+  $* <"*" >>EOO
+  '*'
+  <newline>
+  EOO
+
+  : followed
+  :
+  $* <"*abc" >>EOO
+  '*'
+  'abc'
+  <newline>
+  EOO
+}
+
+: working-dir
+:
+{
+  : only
+  :
+  $* <"~" >>EOO
+  '~'
+  <newline>
+  EOO
+
+  : followed
+  :
+  $* <"~123" >>EOO
+  '~'
+  '123'
+  <newline>
+  EOO
+}
+
+: arg
+:
+{
+  : only
+  :
+  $* <"0" >>EOO
+  '0'
+  <newline>
+  EOO
+
+  : followed
+  :
+  $* <"1abc" >>EOO
+  '1'
+  'abc'
+  <newline>
+  EOO
+
+  : multi-digit
+  :
+  $* <"10" 2>>EOE != 0
+  stdin:1:1: error: multi-digit special variable name
+  EOE
+}
diff --git a/libbuild2/test/script/lexer.cxx b/libbuild2/test/script/lexer.cxx
new file mode 100644
index 0000000..75c04c8
--- /dev/null
+++ b/libbuild2/test/script/lexer.cxx
@@ -0,0 +1,551 @@
+// file      : libbuild2/test/script/lexer.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/test/script/lexer.hxx>
+
+#include <cstring> // strchr()
+
+using namespace std;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      using type = token_type;
+
+      void lexer::
+      mode (base_mode m, char ps, optional<const char*> esc)
+      {
+        const char* s1 (nullptr);
+        const char* s2 (nullptr);
+        bool s (true);
+        bool n (true);
+        bool q (true);
+
+        if (!esc)
+        {
+          assert (!state_.empty ());
+          esc = state_.top ().escapes;
+        }
+
+        switch (m)
+        {
+        case lexer_mode::command_line:
+          {
+            s1 = ":;=!|&<> $(#\t\n";
+            s2 = "  ==          ";
+            break;
+          }
+        case lexer_mode::first_token:
+          {
+            // First token on the script line. Like command_line but
+            // recognizes leading '.+-{}' as tokens as well as variable
+            // assignments as separators.
+            //
+            // Note that to recognize only leading '.+-{}' we shouldn't add
+            // them to the separator strings.
+            //
+            s1 = ":;=+!|&<> $(#\t\n";
+            s2 = "   ==          ";
+            break;
+          }
+        case lexer_mode::second_token:
+          {
+            // Second token on the script line. Like command_line but
+            // recognizes leading variable assignments.
+            //
+            // Note that to recognize only leading assignments we shouldn't
+            // add them to the separator strings (so this is identical to
+            // command_line).
+            //
+            s1 = ":;=!|&<> $(#\t\n";
+            s2 = "  ==          ";
+            break;
+          }
+        case lexer_mode::variable_line:
+          {
+            // Like value except we recognize ';' and don't recognize '{'.
+            // Note that we don't recognize ':' since having a trailing
+            // variable assignment is illegal.
+            //
+            s1 = "; $([]#\t\n";
+            s2 = "         ";
+            break;
+          }
+
+        case lexer_mode::command_expansion:
+          {
+            // Note that whitespaces are not word separators in this mode.
+            //
+            s1 = "|&<>";
+            s2 = "    ";
+            s = false;
+            break;
+          }
+        case lexer_mode::here_line_single:
+          {
+            // This one is like a single-quoted string except it treats
+            // newlines as a separator. We also treat quotes as literals.
+            //
+            // Note that it might be tempting to enable line continuation
+            // escapes. However, we will then have to also enable escaping of
+            // the backslash, which makes it a lot less tempting.
+            //
+            s1 = "\n";
+            s2 = " ";
+            esc = ""; // Disable escape sequences.
+            s = false;
+            q = false;
+            break;
+          }
+        case lexer_mode::here_line_double:
+          {
+            // This one is like a double-quoted string except it treats
+            // newlines as a separator. We also treat quotes as literals.
+            //
+            s1 = "$(\n";
+            s2 = "   ";
+            s = false;
+            q = false;
+            break;
+          }
+        case lexer_mode::description_line:
+          {
+            // This one is like a single-quoted string and has an ad hoc
+            // implementation.
+            //
+            break;
+          }
+        default:
+          {
+            // Make sure pair separators are only enabled where we expect
+            // them.
+            //
+            // @@ Should we disable pair separators in the eval mode?
+            //
+            assert (ps == '\0' ||
+                    m == lexer_mode::eval ||
+                    m == lexer_mode::attribute);
+
+            base_lexer::mode (m, ps, esc);
+            return;
+          }
+        }
+
+        assert (ps == '\0');
+        state_.push (state {m, ps, s, n, q, *esc, s1, s2});
+      }
+
+      token lexer::
+      next ()
+      {
+        token r;
+
+        switch (state_.top ().mode)
+        {
+        case lexer_mode::command_line:
+        case lexer_mode::first_token:
+        case lexer_mode::second_token:
+        case lexer_mode::variable_line:
+        case lexer_mode::command_expansion:
+        case lexer_mode::here_line_single:
+        case lexer_mode::here_line_double:
+          r = next_line ();
+          break;
+        case lexer_mode::description_line:
+          r = next_description ();
+          break;
+        default:
+          r = base_lexer::next ();
+          break;
+        }
+
+        if (r.qtype != quote_type::unquoted)
+          ++quoted_;
+
+        return r;
+      }
+
+      token lexer::
+      next_line ()
+      {
+        bool sep (skip_spaces ());
+
+        xchar c (get ());
+        uint64_t ln (c.line), cn (c.column);
+
+        if (eos (c))
+          return token (type::eos, sep, ln, cn, token_printer);
+
+        state st (state_.top ()); // Make copy (see first/second_token).
+        lexer_mode m (st.mode);
+
+        auto make_token = [&sep, &m, ln, cn] (type t, string v = string ())
+        {
+          bool q (m == lexer_mode::here_line_double);
+
+          return token (t, move (v), sep,
+                        (q ? quote_type::double_ : quote_type::unquoted), q,
+                        ln, cn,
+                        token_printer);
+        };
+
+        auto make_token_with_modifiers =
+          [&make_token, this] (type t,
+                               const char* mods,           // To recorgnize.
+                               const char* stop = nullptr) // To stop after.
+        {
+          string v;
+          if (mods != nullptr)
+          {
+            for (xchar p (peek ());
+                 (strchr (mods, p) != nullptr &&      // Modifier.
+                  strchr (v.c_str (), p) == nullptr); // Not already seen.
+                 p = peek ())
+            {
+              get ();
+              v += p;
+
+              if (stop != nullptr && strchr (stop, p) != nullptr)
+                break;
+            }
+          }
+
+          return make_token (t, move (v));
+        };
+
+        // Expire certain modes at the end of the token. Do it early in case
+        // we push any new mode (e.g., double quote).
+        //
+        if (m == lexer_mode::first_token || m == lexer_mode::second_token)
+          state_.pop ();
+
+        // NOTE: remember to update mode() if adding new special characters.
+
+        if (m != lexer_mode::command_expansion)
+        {
+          switch (c)
+          {
+          case '\n':
+            {
+              // Expire variable value mode at the end of the line.
+              //
+              if (m == lexer_mode::variable_line)
+                state_.pop ();
+
+              sep = true; // Treat newline as always separated.
+              return make_token (type::newline);
+            }
+          }
+        }
+
+        if (m != lexer_mode::here_line_single)
+        {
+          switch (c)
+          {
+            // Variable expansion, function call, and evaluation context.
+            //
+          case '$': return make_token (type::dollar);
+          case '(': return make_token (type::lparen);
+          }
+        }
+
+
+        if (m == lexer_mode::variable_line)
+        {
+          switch (c)
+          {
+            // Attributes.
+            //
+          case '[': return make_token (type::lsbrace);
+          case ']': return make_token (type::rsbrace);
+          }
+        }
+
+        // Line separators.
+        //
+        if (m == lexer_mode::command_line ||
+            m == lexer_mode::first_token  ||
+            m == lexer_mode::second_token ||
+            m == lexer_mode::variable_line)
+        {
+          switch (c)
+          {
+          case ';': return make_token (type::semi);
+          }
+        }
+
+        if (m == lexer_mode::command_line ||
+            m == lexer_mode::first_token  ||
+            m == lexer_mode::second_token)
+        {
+          switch (c)
+          {
+          case ':': return make_token (type::colon);
+          }
+        }
+
+        // Command line operator/separators.
+        //
+        if (m == lexer_mode::command_line ||
+            m == lexer_mode::first_token  ||
+            m == lexer_mode::second_token)
+        {
+          switch (c)
+          {
+            // Comparison (==, !=).
+            //
+          case '=':
+          case '!':
+            {
+              if (peek () == '=')
+              {
+                get ();
+                return make_token (c == '=' ? type::equal : type::not_equal);
+              }
+            }
+          }
+        }
+
+        // Command operators/separators.
+        //
+        if (m == lexer_mode::command_line ||
+            m == lexer_mode::first_token  ||
+            m == lexer_mode::second_token ||
+            m == lexer_mode::command_expansion)
+        {
+          switch (c)
+          {
+            // |, ||
+            //
+          case '|':
+            {
+              if (peek () == '|')
+              {
+                get ();
+                return make_token (type::log_or);
+              }
+              else
+                return make_token (type::pipe);
+            }
+            // &, &&
+            //
+          case '&':
+            {
+              xchar p (peek ());
+
+              if (p == '&')
+              {
+                get ();
+                return make_token (type::log_and);
+              }
+
+              // These modifiers are mutually exclusive so stop after seeing
+              // either one.
+              //
+              return make_token_with_modifiers (type::clean, "!?", "!?");
+            }
+            // <
+            //
+          case '<':
+            {
+              type r (type::in_str);
+              xchar p (peek ());
+
+              if (p == '|' || p == '-' || p == '<')
+              {
+                get ();
+
+                switch (p)
+                {
+                case '|': return make_token (type::in_pass);
+                case '-': return make_token (type::in_null);
+                case '<':
+                  {
+                    r = type::in_doc;
+                    p = peek ();
+
+                    if (p == '<')
+                    {
+                      get ();
+                      r = type::in_file;
+                    }
+                    break;
+                  }
+                }
+              }
+
+              // Handle modifiers.
+              //
+              const char* mods (nullptr);
+              switch (r)
+              {
+              case type::in_str:
+              case type::in_doc: mods = ":/"; break;
+              }
+
+              return make_token_with_modifiers (r, mods);
+            }
+            // >
+            //
+          case '>':
+            {
+              type r (type::out_str);
+              xchar p (peek ());
+
+              if (p == '|' || p == '-' || p == '!' || p == '&' ||
+                  p == '=' || p == '+' || p == '>')
+              {
+                get ();
+
+                switch (p)
+                {
+                case '|': return make_token (type::out_pass);
+                case '-': return make_token (type::out_null);
+                case '!': return make_token (type::out_trace);
+                case '&': return make_token (type::out_merge);
+                case '=': return make_token (type::out_file_ovr);
+                case '+': return make_token (type::out_file_app);
+                case '>':
+                  {
+                    r = type::out_doc;
+                    p = peek ();
+
+                    if (p == '>')
+                    {
+                      get ();
+                      r = type::out_file_cmp;
+                    }
+                    break;
+                  }
+                }
+              }
+
+              // Handle modifiers.
+              //
+              const char* mods (nullptr);
+              const char* stop (nullptr);
+              switch (r)
+              {
+              case type::out_str:
+              case type::out_doc:  mods = ":/~"; stop = "~"; break;
+              }
+
+              return make_token_with_modifiers (r, mods, stop);
+            }
+          }
+        }
+
+        // Dot, plus/minus, and left/right curly braces.
+        //
+        if (m == lexer_mode::first_token)
+        {
+          switch (c)
+          {
+          case '.': return make_token (type::dot);
+          case '+': return make_token (type::plus);
+          case '-': return make_token (type::minus);
+          case '{': return make_token (type::lcbrace);
+          case '}': return make_token (type::rcbrace);
+          }
+        }
+
+        // Variable assignment (=, +=, =+).
+        //
+        if (m == lexer_mode::second_token)
+        {
+          switch (c)
+          {
+          case '=':
+            {
+              if (peek () == '+')
+              {
+                get ();
+                return make_token (type::prepend);
+              }
+              else
+                return make_token (type::assign);
+            }
+          case '+':
+            {
+              if (peek () == '=')
+              {
+                get ();
+                return make_token (type::append);
+              }
+            }
+          }
+        }
+
+        // Otherwise it is a word.
+        //
+        unget (c);
+        return word (st, sep);
+      }
+
+      token lexer::
+      next_description ()
+      {
+        xchar c (peek ());
+
+        if (eos (c))
+          fail (c) << "expected newline at the end of description line";
+
+        uint64_t ln (c.line), cn (c.column);
+
+        if (c == '\n')
+        {
+          get ();
+          state_.pop (); // Expire the description mode.
+          return token (type::newline, true, ln, cn, token_printer);
+        }
+
+        string lexeme;
+
+        // For now no line continutions though we could support them.
+        //
+        for (; !eos (c) && c != '\n'; c = peek ())
+        {
+          get ();
+          lexeme += c;
+        }
+
+        return token (move (lexeme),
+                      false,
+                      quote_type::unquoted, false,
+                      ln, cn);
+      }
+
+      token lexer::
+      word (state st, bool sep)
+      {
+        lexer_mode m (st.mode);
+
+        // Customized implementation that handles special variable names ($*,
+        // $N, $~, $@).
+        //
+        if (m != lexer_mode::variable)
+          return base_lexer::word (st, sep);
+
+        xchar c (peek ());
+
+        if (c != '*' && c != '~' && c != '@' && !digit (c))
+          return base_lexer::word (st, sep);
+
+        get ();
+
+        if (digit (c) && digit (peek ()))
+          fail (c) << "multi-digit special variable name";
+
+        state_.pop (); // Expire the variable mode.
+        return token (string (1, c),
+                      sep,
+                      quote_type::unquoted, false,
+                      c.line, c.column);
+      }
+    }
+  }
+}
diff --git a/libbuild2/test/script/lexer.hxx b/libbuild2/test/script/lexer.hxx
new file mode 100644
index 0000000..d96e91b
--- /dev/null
+++ b/libbuild2/test/script/lexer.hxx
@@ -0,0 +1,94 @@
+// file      : libbuild2/test/script/lexer.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_TEST_SCRIPT_LEXER_HXX
+#define LIBBUILD2_TEST_SCRIPT_LEXER_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/lexer.hxx>
+
+#include <libbuild2/test/script/token.hxx>
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      struct lexer_mode: build2::lexer_mode
+      {
+        using base_type = build2::lexer_mode;
+
+        enum
+        {
+          command_line = base_type::value_next,
+          first_token,     // Expires at the end of the token.
+          second_token,    // Expires at the end of the token.
+          variable_line,   // Expires at the end of the line.
+          command_expansion,
+          here_line_single,
+          here_line_double,
+          description_line // Expires at the end of the line.
+        };
+
+        lexer_mode () = default;
+        lexer_mode (value_type v): base_type (v) {}
+        lexer_mode (base_type v): base_type (v) {}
+      };
+
+      class lexer: public build2::lexer
+      {
+      public:
+        using base_lexer = build2::lexer;
+        using base_mode = build2::lexer_mode;
+
+        lexer (istream& is,
+               const path& name,
+               lexer_mode m,
+               const char* escapes = nullptr)
+            : base_lexer (is,
+                          name,
+                          1       /* line */,
+                          nullptr /* escapes */,
+                          false   /* set_mode */)
+        {
+          mode (m, '\0', escapes);
+        }
+
+        virtual void
+        mode (base_mode,
+              char = '\0',
+              optional<const char*> = nullopt) override;
+
+        // Number of quoted (double or single) tokens since last reset.
+        //
+        size_t
+        quoted () const {return quoted_;}
+
+        void
+        reset_quoted (size_t q) {quoted_ = q;}
+
+        virtual token
+        next () override;
+
+      protected:
+        token
+        next_line ();
+
+        token
+        next_description ();
+
+        virtual token
+        word (state, bool) override;
+
+      protected:
+        size_t quoted_;
+      };
+    }
+  }
+}
+
+#endif // LIBBUILD2_TEST_SCRIPT_LEXER_HXX
diff --git a/libbuild2/test/script/lexer.test.cxx b/libbuild2/test/script/lexer.test.cxx
new file mode 100644
index 0000000..5a421b8
--- /dev/null
+++ b/libbuild2/test/script/lexer.test.cxx
@@ -0,0 +1,85 @@
+// file      : libbuild2/test/script/lexer.test.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <cassert>
+#include <iostream>
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/test/script/token.hxx>
+#include <libbuild2/test/script/lexer.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      // Usage: argv[0] <lexer-mode>
+      //
+      int
+      main (int argc, char* argv[])
+      {
+        lexer_mode m;
+        {
+          assert (argc == 2);
+          string s (argv[1]);
+
+          if      (s == "command-line")      m = lexer_mode::command_line;
+          else if (s == "first-token")       m = lexer_mode::first_token;
+          else if (s == "second-token")      m = lexer_mode::second_token;
+          else if (s == "variable-line")     m = lexer_mode::variable_line;
+          else if (s == "command-expansion") m = lexer_mode::command_expansion;
+          else if (s == "here-line-single")  m = lexer_mode::here_line_single;
+          else if (s == "here-line-double")  m = lexer_mode::here_line_double;
+          else if (s == "description-line")  m = lexer_mode::description_line;
+          else if (s == "variable")          m = lexer_mode::variable;
+          else                               assert (false);
+        }
+
+        try
+        {
+          cin.exceptions (istream::failbit | istream::badbit);
+
+          // Some modes auto-expire so we need something underneath.
+          //
+          bool u (m == lexer_mode::first_token      ||
+                  m == lexer_mode::second_token     ||
+                  m == lexer_mode::variable_line    ||
+                  m == lexer_mode::description_line ||
+                  m == lexer_mode::variable);
+
+          lexer l (cin, path ("stdin"), u ? lexer_mode::command_line : m);
+          if (u)
+            l.mode (m);
+
+          // No use printing eos since we will either get it or loop forever.
+          //
+          for (token t (l.next ()); t.type != token_type::eos; t = l.next ())
+          {
+            // Print each token on a separate line without quoting operators.
+            //
+            t.printer (cout, t, false);
+            cout << endl;
+          }
+        }
+        catch (const failed&)
+        {
+          return 1;
+        }
+
+        return 0;
+      }
+    }
+  }
+}
+
+int
+main (int argc, char* argv[])
+{
+  return build2::test::script::main (argc, argv);
+}
diff --git a/libbuild2/test/script/parser+cleanup.test.testscript b/libbuild2/test/script/parser+cleanup.test.testscript
new file mode 100644
index 0000000..321664c
--- /dev/null
+++ b/libbuild2/test/script/parser+cleanup.test.testscript
@@ -0,0 +1,58 @@
+# file      : libbuild2/test/script/parser+cleanup.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: always
+:
+$* <<EOI >>EOO
+cmd &file
+EOI
+cmd &file
+EOO
+
+: maybe
+:
+$* <<EOI >>EOO
+cmd &?file
+EOI
+cmd &?file
+EOO
+
+: never
+:
+$* <<EOI >>EOO
+cmd &!file
+EOI
+cmd &!file
+EOO
+
+: empty
+:
+$* <<EOI 2>>EOE != 0
+cmd &""
+EOI
+testscript:1:6: error: empty cleanup path
+EOE
+
+: missed-before
+:
+{
+  : token
+  :
+  : Path missed before command next token
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd & >file
+  EOI
+  testscript:1:7: error: missing cleanup path
+  EOE
+
+  : end
+  : Test path missed before end of command
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd &
+  EOI
+  testscript:1:6: error: missing cleanup path
+  EOE
+}
diff --git a/libbuild2/test/script/parser+command-if.test.testscript b/libbuild2/test/script/parser+command-if.test.testscript
new file mode 100644
index 0000000..7425da2
--- /dev/null
+++ b/libbuild2/test/script/parser+command-if.test.testscript
@@ -0,0 +1,548 @@
+# file      : libbuild2/test/script/parser+command-if.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: if
+:
+{
+  : true
+  :
+  $* <<EOI >>EOO
+  if true foo
+    cmd1
+    cmd2
+  end
+  EOI
+  ? true foo
+  cmd1
+  cmd2
+  EOO
+
+  : false
+  :
+  $* <<EOI >>EOO
+  if false foo
+    cmd1
+    cmd2
+  end
+  EOI
+  ? false foo
+  EOO
+
+  : not-true
+  :
+  $* <<EOI >>EOO
+  if! true foo
+    cmd1
+    cmd2
+  end
+  EOI
+  ? true foo
+  EOO
+
+  : not-false
+  :
+  $* <<EOI >>EOO
+  if! false foo
+    cmd1
+    cmd2
+  end
+  EOI
+  ? false foo
+  cmd1
+  cmd2
+  EOO
+
+  : without-command
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+    cmd
+  end
+  EOI
+  testscript:1:3: error: missing program
+  EOE
+
+  : after-semi
+  :
+  $* -s <<EOI >>EOO
+  cmd1;
+  if true
+    cmd2
+  end
+  EOI
+  {
+    {
+      cmd1
+      ? true
+      cmd2
+    }
+  }
+  EOO
+
+  : setup
+  :
+  $* -s <<EOI >>EOO
+  +if true
+    cmd
+  end
+  EOI
+  {
+    ? true
+    +cmd
+  }
+  EOO
+
+  : tdown
+  :
+  $* -s <<EOI >>EOO
+  -if true
+    cmd
+  end
+  EOI
+  {
+    ? true
+    -cmd
+  }
+  EOO
+}
+
+: elif
+:
+{
+  : true
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  elif true
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  ? true
+  cmd3
+  cmd4
+  EOO
+
+  : false
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  elif false
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  ? false
+  EOO
+
+  : not-true
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  elif! true
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  ? true
+  EOO
+
+  : not-false
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  elif! false
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  ? false
+  cmd3
+  cmd4
+  EOO
+
+  : without-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  elif true
+    cmd
+  end
+  EOI
+  testscript:2:1: error: 'elif' without preceding 'if'
+  EOE
+
+  : not-without-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  elif! true
+    cmd
+  end
+  EOI
+  testscript:2:1: error: 'elif!' without preceding 'if'
+  EOE
+
+  : after-else
+  :
+  $* <<EOI 2>>EOE != 0
+  if false
+    cmd
+  else
+    cmd
+  elif true
+    cmd
+  end
+  EOI
+  testscript:5:1: error: 'elif' after 'else'
+  EOE
+}
+
+: else
+:
+{
+  : true
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    cmd2
+  else
+    cmd3
+    cmd4
+  end
+  EOI
+  ? false
+  cmd3
+  cmd4
+  EOO
+
+  : false
+  :
+  $* <<EOI >>EOO
+  if true
+    cmd1
+    cmd2
+  else
+    cmd3
+    cmd4
+  end
+  EOI
+  ? true
+  cmd1
+  cmd2
+  EOO
+
+  : chain
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd
+    cmd
+  elif false
+    cmd
+    cmd
+  elif false
+    cmd
+    cmd
+  elif true
+    cmd1
+    cmd2
+  elif false
+    cmd
+    cmd
+  else
+    cmd
+    cmd
+  end
+  EOI
+  ? false
+  ? false
+  ? false
+  ? true
+  cmd1
+  cmd2
+  EOO
+
+  : command-after
+  :
+  $* <<EOI 2>>EOE != 0
+  if true
+    cmd
+  else cmd
+    cmd
+  end
+  EOI
+  testscript:3:6: error: expected newline instead of 'cmd'
+  EOE
+
+  : without-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  else
+    cmd
+  end
+  EOI
+  testscript:2:1: error: 'else' without preceding 'if'
+  EOE
+
+  : after-else
+  :
+  $* <<EOI 2>>EOE != 0
+  if false
+    cmd
+  else
+    cmd
+  else
+    cmd
+  end
+  EOI
+  testscript:5:1: error: 'else' after 'else'
+  EOE
+}
+
+: end
+{
+  : without-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  end
+  EOI
+  testscript:2:1: error: 'end' without preceding 'if'
+  EOE
+
+  : before
+  {
+    : semi
+    :
+    $* -s <<EOI >>EOO
+    if true
+      cmd1
+    end;
+    cmd2
+    EOI
+    {
+      {
+        ? true
+        cmd1
+        cmd2
+      }
+    }
+    EOO
+
+    : command
+    :
+    $* <<EOI 2>>EOE != 0
+    if true
+      cmd
+    end cmd
+    EOI
+    testscript:3:5: error: expected newline instead of 'cmd'
+    EOE
+
+    : colon
+    :
+    $* -s <<EOI >>EOO
+    if true
+      cmd1
+      cmd2
+    end : test
+    EOI
+    {
+      : id:test
+      {
+        ? true
+        cmd1
+        cmd2
+      }
+    }
+    EOO
+  }
+}
+
+: nested
+:
+{
+  : take
+  :
+  $* <<EOI >>EOO
+  if true
+    cmd1
+    if false
+      cmd
+    elif false
+      if true
+        cmd
+      end
+    else
+      cmd2
+    end
+    cmd3
+  end
+  EOI
+  ? true
+  cmd1
+  ? false
+  ? false
+  cmd2
+  cmd3
+  EOO
+
+  : skip
+  :
+  $* <<EOI >>EOO
+  if false
+    cmd1
+    if false
+      cmd
+    elif false
+      if true
+        cmd
+      end
+    else
+      cmd2
+    end
+    cmd3
+  else
+    cmd
+  end
+  EOI
+  ? false
+  cmd
+  EOO
+}
+
+: contained
+{
+  : semi
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+    cmd;
+    cmd
+  end
+  EOI
+  testscript:2:3: error: ';' inside 'if'
+  EOE
+
+  : colon-leading
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+    : foo
+    cmd
+  end
+  EOI
+  testscript:2:3: error: description inside 'if'
+  EOE
+
+  : colon-trailing
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+    cmd : foo
+  end
+  EOI
+  testscript:2:3: error: description inside 'if'
+  EOE
+
+  : eos
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+  EOI
+  testscript:2:1: error: expected closing 'end'
+  EOE
+
+  : scope
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+    cmd
+    {
+    }
+  end
+  EOI
+  testscript:3:3: error: expected closing 'end'
+  EOE
+
+  : setup
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+    +cmd
+  end
+  EOI
+  testscript:2:3: error: setup command inside 'if'
+  EOE
+
+  : tdown
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+    -cmd
+  end
+  EOI
+  testscript:2:3: error: teardown command inside 'if'
+  EOE
+}
+
+: line-index
+:
+$* -l <<EOI >>EOO
+if false
+  cmd
+  if true
+    cmd
+  end
+  cmd
+elif false
+  cmd
+else
+  cmd
+end
+EOI
+? false # 1
+? false # 6
+cmd # 8
+EOO
+
+: var
+:
+$* <<EOI >>EOO
+if true
+  x = foo
+else
+  x = bar
+end;
+cmd $x
+EOI
+? true
+cmd foo
+EOO
+
+: leading-and-trailing-description
+:
+$* <<EOI 2>>EOE != 0
+: foo
+if true
+  cmd
+end : bar
+EOI
+testscript:4:1: error: both leading and trailing descriptions
+EOE
diff --git a/libbuild2/test/script/parser+command-re-parse.test.testscript b/libbuild2/test/script/parser+command-re-parse.test.testscript
new file mode 100644
index 0000000..f5a67f3
--- /dev/null
+++ b/libbuild2/test/script/parser+command-re-parse.test.testscript
@@ -0,0 +1,12 @@
+# file      : libbuild2/test/script/parser+command-re-parse.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: double-quote
+:
+$* <<EOI >>EOO
+x = cmd \">-\" "'<-'"
+$x
+EOI
+cmd '>-' '<-'
+EOO
diff --git a/libbuild2/test/script/parser+description.test.testscript b/libbuild2/test/script/parser+description.test.testscript
new file mode 100644
index 0000000..d17a69f
--- /dev/null
+++ b/libbuild2/test/script/parser+description.test.testscript
@@ -0,0 +1,486 @@
+# file      : libbuild2/test/script/parser+description.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: id
+:
+{
+  : lead
+  :
+  $* <<EOI >>EOO
+  : foo
+  cmd
+  EOI
+  : id:foo
+  cmd
+  EOO
+
+  : trail
+  :
+  $* <<EOI >>EOO
+  cmd : foo
+  EOI
+  : id:foo
+  cmd
+  EOO
+
+  : dup
+  : Id uniqueness
+  :
+  {
+    : test
+    :
+    {
+      : test
+      :
+      $* <<EOI 2>>EOE != 0
+      : foo
+      cmd
+      : foo
+      cmd
+      EOI
+      testscript:3:1: error: duplicate id foo
+        testscript:1:1: info: previously used here
+      EOE
+
+      : group
+      :
+      $* <<EOI 2>>EOE != 0
+      : foo
+      cmd
+      : foo
+      {
+        cmd
+        cmd
+      }
+      EOI
+      testscript:3:1: error: duplicate id foo
+        testscript:1:1: info: previously used here
+      EOE
+
+      : derived
+      :
+      $* <<EOI 2>>EOE != 0
+      : 3
+      cmd
+      cmd
+      EOI
+      testscript:3:1: error: duplicate id 3
+        testscript:1:1: info: previously used here
+      EOE
+    }
+
+    : group
+    :
+    {
+      : test
+      :
+      $* <<EOI 2>>EOE != 0
+      : foo
+      {
+        cmd
+        cmd
+      }
+      : foo
+      cmd
+      EOI
+      testscript:6:1: error: duplicate id foo
+        testscript:1:1: info: previously used here
+      EOE
+
+      : group
+      :
+      $* <<EOI 2>>EOE != 0
+      : foo
+      {
+        cmd
+        cmd
+      }
+      : foo
+      {
+        cmd
+        cmd
+      }
+      EOI
+      testscript:6:1: error: duplicate id foo
+        testscript:1:1: info: previously used here
+      EOE
+
+      : derived
+      :
+      $* <<EOI 2>>EOE != 0
+      : 3
+      cmd
+      {
+        cmd
+        cmd
+      }
+      EOI
+      testscript:3:1: error: duplicate id 3
+        testscript:1:1: info: previously used here
+      EOE
+    }
+  }
+}
+
+: summary
+{
+  : lead
+  :
+  $* <<EOI >>EOO
+  : foo bar
+  cmd
+  EOI
+  : sm:foo bar
+  cmd
+  EOO
+
+  : trail
+  :
+  $* <<EOI >>EOO
+  cmd: foo bar
+  EOI
+  : sm:foo bar
+  cmd
+  EOO
+
+  : id
+  :
+  $* <<EOI >>EOO
+  : foo-bar
+  : foo bar
+  cmd
+  EOI
+  : id:foo-bar
+  : sm:foo bar
+  cmd
+  EOO
+}
+
+: details
+{
+  : id
+  :
+  $* <<EOI >>EOO
+  : foo-bar
+  :
+  : foo bar
+  : bar baz
+  cmd
+  EOI
+  : id:foo-bar
+  :
+  : foo bar
+  : bar baz
+  cmd
+  EOO
+
+  : summary
+  :
+  {
+    : only
+    :
+    $* <<EOI >>EOO
+    : foo bar
+    :
+    : foo bar
+    : bar baz
+    cmd
+    EOI
+    : sm:foo bar
+    :
+    : foo bar
+    : bar baz
+    cmd
+    EOO
+
+    : assumed
+    :
+    $* <<EOI >>EOO
+    : foo bar
+    : bar baz
+    cmd
+    EOI
+    : foo bar
+    : bar baz
+    cmd
+    EOO
+
+    : id
+    :
+    $* <<EOI >>EOO
+    : foo-bar
+    : foo bar
+    :
+    : foo bar
+    : bar baz
+    cmd
+    EOI
+    : id:foo-bar
+    : sm:foo bar
+    :
+    : foo bar
+    : bar baz
+    cmd
+    EOO
+
+    : id-assumed
+    :
+    $* <<EOI >>EOO
+    : foo-bar
+    : bar baz
+    : baz fox
+    cmd
+    EOI
+    : foo-bar
+    : bar baz
+    : baz fox
+    cmd
+    EOO
+  }
+}
+
+: legal
+:
+: Legal places for description.
+:
+{
+  : var
+  :
+  $* <<EOI >>EOO
+  : foo bar
+  x = y;
+  cmd $x
+  EOI
+  : sm:foo bar
+  cmd y
+  EOO
+}
+
+: illegal
+:
+: Illegal places for description.
+:
+{
+  : eof
+  :
+  $* <": foo" 2>>EOE != 0
+  testscript:2:1: error: description before <end of file>
+  EOE
+
+  : rcbrace
+  :
+  $* <<EOI 2>>EOE != 0
+  {
+    cmd
+    : foo
+  }
+  EOI
+  testscript:4:1: error: description before '}'
+  EOE
+
+  : setup
+  :
+  $* <<EOI 2>>EOE != 0
+  : foo
+  +cmd
+  EOI
+  testscript:2:1: error: description before setup command
+  EOE
+
+  : tdown
+  :
+  $* <<EOI 2>>EOE != 0
+  : foo
+  -cmd
+  EOI
+  testscript:2:1: error: description before teardown command
+  EOE
+
+  : var
+  :
+  $* <<EOI 2>>EOE != 0
+  : foo
+  x = y
+  EOI
+  testscript:2:1: error: description before setup/teardown variable
+  EOE
+
+  : var-if
+  :
+  $* <<EOI 2>>EOE != 0
+  : foo
+  if true
+    x = y
+  end
+  EOI
+  testscript:2:1: error: description before/after setup/teardown variable-if
+  EOE
+
+  : var-if-after
+  :
+  $* <<EOI 2>>EOE != 0
+  if true
+    x = y
+  end : foo
+  EOI
+  testscript:1:1: error: description before/after setup/teardown variable-if
+  EOE
+
+  : test
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd1;
+  : foo
+  cmd2
+  EOI
+  testscript:2:1: error: description inside test
+  EOE
+}
+
+: test-scope
+:
+: Interaction with test scope merging.
+:
+{
+  : both
+  :
+  : No merge since both have description.
+  :
+  $* -s -i <<EOI >>EOO
+  : foo
+  {
+    : bar
+    cmd
+  }
+  EOI
+  {
+    : id:foo
+    { # foo
+      : id:bar
+      { # foo/bar
+        cmd
+      }
+    }
+  }
+  EOO
+
+  : test
+  :
+  : No merge since test has description.
+  :
+  $* -s -i <<EOI >>EOO
+  {
+    : foo-bar
+    : foo bar
+    cmd
+  }
+  EOI
+  {
+    { # 1
+      : id:foo-bar
+      : sm:foo bar
+      { # 1/foo-bar
+        cmd
+      }
+    }
+  }
+  EOO
+
+  : group
+  :
+  $* -s -i <<EOI >>EOO
+  : foo-bar
+  : foo bar
+  {
+    cmd
+  }
+  EOI
+  {
+    : id:foo-bar
+    : sm:foo bar
+    { # foo-bar
+      cmd
+    }
+  }
+  EOO
+}
+
+: blanks
+:
+$* <<EOI >>EOO
+:
+:
+: foo bar
+: bar baz
+:
+: baz fox
+:
+:
+cmd
+EOI
+: foo bar
+: bar baz
+:
+: baz fox
+cmd
+EOO
+
+: strip
+:
+$* <<EOI >>EOO
+:         foo-bar
+:         bar baz
+:
+:           baz fox
+: fox biz
+:biz buz
+:
+cmd
+EOI
+: id:foo-bar
+: sm:bar baz
+:
+:   baz fox
+:  fox biz
+: biz buz
+cmd
+EOO
+
+: trail-compound
+:
+$* <<EOI >>EOO
+cmd1;
+cmd2: foo
+EOI
+: id:foo
+cmd1
+cmd2
+EOO
+
+: empty
+:
+$* <<EOI 2>>EOE != 0
+:
+:
+cmd
+EOI
+testscript:1:1: error: empty description
+EOE
+
+: trail-empty
+:
+$* <<EOI 2>>EOE != 0
+cmd:
+EOI
+testscript:1:4: error: empty description
+EOE
+
+: both
+:
+$* <<EOI 2>>EOE != 0
+: foo
+cmd : bar
+EOI
+testscript:2:1: error: both leading and trailing descriptions
+EOE
diff --git a/libbuild2/test/script/parser+directive.test.testscript b/libbuild2/test/script/parser+directive.test.testscript
new file mode 100644
index 0000000..9d04ce7
--- /dev/null
+++ b/libbuild2/test/script/parser+directive.test.testscript
@@ -0,0 +1,74 @@
+# file      : libbuild2/test/script/parser+directive.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: not-directive
+:
+$* <<EOI >>EOO
+x = x
+".include" foo.testscript
+\.include foo.testscript
+EOI
+.include foo.testscript
+.include foo.testscript
+EOO
+
+: expected-name
+:
+$* <<EOI 2>>EOE != 0
+.$
+EOI
+testscript:1:2: error: expected directive name instead of '$'
+EOE
+
+: unknown-name
+:
+$* <<EOI 2>>EOE != 0
+.bogus
+EOI
+testscript:1:2: error: unknown directive 'bogus'
+EOE
+
+: separated
+:
+touch foo.testscript;
+$* <<EOI
+.  include foo.testscript
+EOI
+
+: not-separated
+:
+touch foo.testscript;
+$* <<EOI
+x = foo.testscript
+.include$x
+EOI
+
+: var-expansion
+:
+cat <<EOI >="foo-$(build.verson.project).testscript";
+cmd
+EOI
+$* <<EOI >>EOO
+.include "foo-$(build.verson.project).testscript"
+EOI
+cmd
+EOO
+
+: after-semi
+:
+$* <<EOI 2>>EOE != 0
+cmd;
+.include foo.testscript
+EOI
+testscript:2:1: error: directive after ';'
+EOE
+
+: semi-after
+:
+$* <<EOI 2>>EOE != 0
+.include foo.testscript;
+cmd
+EOI
+testscript:1:24: error: ';' after directive
+EOE
diff --git a/libbuild2/test/script/parser+exit.test.testscript b/libbuild2/test/script/parser+exit.test.testscript
new file mode 100644
index 0000000..284e9a7
--- /dev/null
+++ b/libbuild2/test/script/parser+exit.test.testscript
@@ -0,0 +1,27 @@
+# file      : libbuild2/test/script/parser+exit.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: eq
+:
+$* <<EOI >>EOO
+cmd == 1
+EOI
+cmd == 1
+EOO
+
+: ne
+:
+$* <<EOI >>EOO
+cmd!=1
+EOI
+cmd != 1
+EOO
+
+: end
+:
+$* <<EOI 2>>EOE != 0
+cmd != 1 <"foo"
+EOI
+testscript:1:10: error: unexpected '<' after command exit status
+EOE
diff --git a/libbuild2/test/script/parser+expansion.test.testscript b/libbuild2/test/script/parser+expansion.test.testscript
new file mode 100644
index 0000000..7ea92f9
--- /dev/null
+++ b/libbuild2/test/script/parser+expansion.test.testscript
@@ -0,0 +1,36 @@
+# file      : libbuild2/test/script/parser+expansion.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: quote
+:
+: Make sure everything expanded as strings.
+:
+$* <<EOI >>EOO
+x = dir/ proj% proj%name proj%proj%dir/type{name   name   {name}}
+cmd dir/ proj% proj%name proj%proj%dir/type{name   name   {name}}
+cmd $x
+EOI
+cmd dir/ proj% proj%name proj%proj%dir/type{name name {name}}
+cmd dir/ proj% proj%name proj%proj%dir/type{name name {name}}
+EOO
+
+: unterm-quoted-seq
+:
+$* <<EOI 2>>EOE != 0
+x = "'a bc"
+cmd xy$x
+EOI
+<string>:1:8: error: unterminated single-quoted sequence
+  testscript:2:5: info: while parsing string 'xy'a bc'
+EOE
+
+: invalid-redirect
+:
+$* <<EOI 2>>EOE != 0
+x = "1>&a"
+cmd $x
+EOI
+<string>:1:4: error: stdout merge redirect file descriptor must be 2
+  testscript:2:5: info: while parsing string '1>&a'
+EOE
diff --git a/libbuild2/test/script/parser+here-document.test.testscript b/libbuild2/test/script/parser+here-document.test.testscript
new file mode 100644
index 0000000..00f3fbd
--- /dev/null
+++ b/libbuild2/test/script/parser+here-document.test.testscript
@@ -0,0 +1,213 @@
+# file      : libbuild2/test/script/parser+here-document.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: end-marker
+:
+{
+  : missing-newline
+  :
+  $* <'cmd <<' 2>>EOE != 0
+  testscript:1:7: error: expected here-document end marker
+  EOE
+
+  : missing-exit
+  :
+  $* <'cmd << != 0' 2>>EOE != 0
+  testscript:1:8: error: expected here-document end marker
+  EOE
+
+  : missing-empty
+  :
+  $* <'cmd <<""' 2>>EOE != 0
+  testscript:1:7: error: expected here-document end marker
+  EOE
+
+  : unseparated-expansion
+  :
+  $* <'cmd <<FOO$foo' 2>>EOE != 0
+  testscript:1:10: error: here-document end marker must be literal
+  EOE
+
+  : quoted-single-partial
+  :
+  $* <"cmd <<F'O'O" 2>>EOE != 0
+  testscript:1:7: error: partially-quoted here-document end marker
+  EOE
+
+  : quoted-double-partial
+  :
+  $* <'cmd <<"FO"O' 2>>EOE != 0
+  testscript:1:7: error: partially-quoted here-document end marker
+  EOE
+
+  : quoted-mixed
+  :
+  $* <"cmd <<\"FO\"'O'" 2>>EOE != 0
+  testscript:1:7: error: partially-quoted here-document end marker
+  EOE
+
+  : unseparated
+  :
+  $* <<EOI >>EOO
+  cmd <<EOF!=0
+  foo
+  EOF
+  EOI
+  cmd <<EOF != 0
+  foo
+  EOF
+  EOO
+
+  : quoted-single
+  :
+  $* <<EOI >>EOO
+  cmd <<'EOF'
+  foo
+  EOF
+  EOI
+  cmd <<EOF
+  foo
+  EOF
+  EOO
+
+  : quoted-double
+  :
+  $* <<EOI >>EOO
+  cmd <<"EOF"
+  foo
+  EOF
+  EOI
+  cmd <<EOF
+  foo
+  EOF
+  EOO
+}
+
+: indent
+:
+{
+  : basic
+  :
+  $* <<EOI >>EOO
+  cmd <<EOF
+    foo
+     bar
+         baz
+    EOF
+  EOI
+  cmd <<EOF
+  foo
+   bar
+       baz
+  EOF
+  EOO
+
+  : blank
+  :
+  $* <<EOI >>EOO
+  cmd <<EOF
+    foo
+
+
+    bar
+    EOF
+  EOI
+  cmd <<EOF
+  foo
+
+
+  bar
+  EOF
+  EOO
+
+  : non-ws-prefix
+  :
+  $* <<EOI >>EOO
+  cmd <<EOF
+   x EOF
+  EOF
+  EOI
+  cmd <<EOF
+   x EOF
+  EOF
+  EOO
+
+  : whole-token
+  : Test the case where the indentation is a whole token
+  :
+  $* <<EOI >>EOO
+  x = foo bar
+  cmd <<"EOF"
+    $x
+    EOF
+  EOI
+  cmd <<EOF
+  foo bar
+  EOF
+  EOO
+
+  : long-line
+  : Test the case where the line contains multiple tokens
+  :
+  $* <<EOI >>EOO
+  x = foo
+  cmd <<"EOF"
+     $x bar $x
+    EOF
+  EOI
+  cmd <<EOF
+   foo bar foo
+  EOF
+  EOO
+
+  : unindented
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd <<EOF
+   bar
+    EOF
+  EOI
+  testscript:2:1: error: unindented here-document line
+  EOE
+}
+
+: blank
+:
+$* <<EOI >>EOO
+cmd <<EOF
+
+foo
+
+bar
+
+EOF
+EOI
+cmd <<EOF
+
+foo
+
+bar
+
+EOF
+EOO
+
+: quote
+:
+: Note: they are still recognized in eval contexts.
+:
+$* <<EOI >>EOO
+cmd <<"EOF"
+'single'
+"double"
+b'o't"h"
+('single' "double")
+EOF
+EOI
+cmd <<EOF
+'single'
+"double"
+b'o't"h"
+single double
+EOF
+EOO
diff --git a/libbuild2/test/script/parser+here-string.test.testscript b/libbuild2/test/script/parser+here-string.test.testscript
new file mode 100644
index 0000000..785951d
--- /dev/null
+++ b/libbuild2/test/script/parser+here-string.test.testscript
@@ -0,0 +1,19 @@
+# file      : libbuild2/test/script/parser+here-string.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: empty
+:
+$* <<EOI >>EOO
+cmd <""
+EOI
+cmd <''
+EOO
+
+: empty-nn
+:
+$* <<EOI >>EOO
+cmd <:""
+EOI
+cmd <:''
+EOO
diff --git a/libbuild2/test/script/parser+include.test.testscript b/libbuild2/test/script/parser+include.test.testscript
new file mode 100644
index 0000000..c86b583
--- /dev/null
+++ b/libbuild2/test/script/parser+include.test.testscript
@@ -0,0 +1,104 @@
+# file      : libbuild2/test/script/parser+include.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: none
+:
+$* <<EOI
+.include
+.include --once
+EOI
+
+: empty
+:
+touch foo.testscript;
+$* <<EOI
+.include foo.testscript
+.include --once foo.testscript
+EOI
+
+: one
+:
+cat <"cmd" >=foo.testscript;
+$* <<EOI >>EOO
+.include foo.testscript
+EOI
+cmd
+EOO
+
+: multiple
+:
+cat <"cmd foo" >=foo.testscript;
+cat <"cmd bar" >=bar.testscript;
+$* <<EOI >>EOO
+.include foo.testscript bar.testscript
+EOI
+cmd foo
+cmd bar
+EOO
+
+: once
+:
+cat <"cmd" >=foo.testscript;
+$* <<EOI >>EOO
+.include foo.testscript
+x
+.include --once foo.testscript
+.include --once bar/../foo.testscript
+y
+.include ../once/foo.testscript
+EOI
+cmd
+x
+y
+cmd
+EOO
+
+: group-id
+:
+cat <<EOI >=foo.testscript;
+{
+  x = b
+}
+EOI
+$* -s -i <<EOI >>EOO
+x = a
+.include foo.testscript
+EOI
+{
+  { # 2-foo-1
+  }
+}
+EOO
+
+: test-id
+:
+cat <<EOI >=foo.testscript;
+cmd
+EOI
+$* -s -i <<EOI >>EOO
+x = a
+.include foo.testscript
+EOI
+{
+  { # 2-foo-1
+    cmd
+  }
+}
+EOO
+
+: invalid-path
+:
+$* <<EOI 2>>EOE != 0
+.include ""
+EOI
+testscript:1:2: error: invalid testscript include path ''
+EOE
+
+: unable-open
+:
+$* <<EOI 2>>~/EOE/ != 0
+.include foo.testscript
+EOI
+/testscript:1:2: error: unable to read testscript foo.testscript: .+/
+EOE
diff --git a/libbuild2/test/script/parser+pipe-expr.test.testscript b/libbuild2/test/script/parser+pipe-expr.test.testscript
new file mode 100644
index 0000000..8b6b4f9
--- /dev/null
+++ b/libbuild2/test/script/parser+pipe-expr.test.testscript
@@ -0,0 +1,133 @@
+# file      : libbuild2/test/script/parser+pipe-expr.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: pipe
+:
+$* <<EOI >>EOO
+cmd1 | cmd2|cmd3
+EOI
+cmd1 | cmd2 | cmd3
+EOO
+
+: log
+:
+$* <<EOI >>EOO
+cmd1 || cmd2&&cmd3
+EOI
+cmd1 || cmd2 && cmd3
+EOO
+
+: pipe-log
+:
+$* <<EOI >>EOO
+cmd1 | cmd2 && cmd3 | cmd4
+EOI
+cmd1 | cmd2 && cmd3 | cmd4
+EOO
+
+: exit
+:
+$* <<EOI >>EOO
+cmd1|cmd2==1&&cmd3!=0|cmd4
+EOI
+cmd1 | cmd2 == 1 && cmd3 != 0 | cmd4
+EOO
+
+: here-doc
+:
+$* <<EOI >>EOO
+cmd1 <<EOI1 | cmd2 >>EOO2 && cmd3 <<EOI3 2>&1 | cmd4 2>>EOE4 >>EOO4
+input
+one
+EOI1
+ouput
+two
+EOO2
+input
+three
+EOI3
+error
+four
+EOE4
+output
+four
+EOO4
+EOI
+cmd1 <<EOI1 | cmd2 >>EOO2 && cmd3 <<EOI3 2>&1 | cmd4 >>EOO4 2>>EOE4
+input
+one
+EOI1
+ouput
+two
+EOO2
+input
+three
+EOI3
+output
+four
+EOO4
+error
+four
+EOE4
+EOO
+
+: leading
+:
+$* <<EOI 2>>EOE != 0
+| cmd
+EOI
+testscript:1:1: error: missing program
+EOE
+
+: trailing
+:
+$* <<EOI 2>>EOE != 0
+cmd &&
+EOI
+testscript:1:7: error: missing program
+EOE
+
+: redirected
+:
+{
+  : input
+  :
+  {
+    : first
+    :
+    $* <<EOI >>EOO
+    cmd1 <foo | cmd2
+    EOI
+    cmd1 <foo | cmd2
+    EOO
+
+    : non-first
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd1 | cmd2 <foo
+    EOI
+    testscript:1:13: error: stdin is both piped and redirected
+    EOE
+  }
+
+  : output
+  :
+  {
+    : last
+    :
+    $* <<EOI >>EOO
+    cmd1 | cmd2 >foo
+    EOI
+    cmd1 | cmd2 >foo
+    EOO
+
+    : non-last
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd1 >foo | cmd2
+    EOI
+    testscript:1:11: error: stdout is both redirected and piped
+    EOE
+  }
+}
diff --git a/libbuild2/test/script/parser+pre-parse.test.testscript b/libbuild2/test/script/parser+pre-parse.test.testscript
new file mode 100644
index 0000000..f98512a
--- /dev/null
+++ b/libbuild2/test/script/parser+pre-parse.test.testscript
@@ -0,0 +1,23 @@
+# file      : libbuild2/test/script/parser+pre-parse.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: attribute
+:
+{
+  : pair
+  :
+  $* <<EOI 2>>EOE != 0
+  x = [foo=bar]
+  EOI
+  testscript:1:5: error: unknown value attribute foo=bar
+  EOE
+
+  : pair-empty
+  :
+  $* <<EOI 2>>EOE != 0
+  x = [foo=]
+  EOI
+  testscript:1:5: error: unknown value attribute foo
+  EOE
+}
diff --git a/libbuild2/test/script/parser+redirect.test.testscript b/libbuild2/test/script/parser+redirect.test.testscript
new file mode 100644
index 0000000..a8691da
--- /dev/null
+++ b/libbuild2/test/script/parser+redirect.test.testscript
@@ -0,0 +1,356 @@
+# file      : libbuild2/test/script/parser+redirect.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+# @@ Add tests for redirects other than trace, here-*, file and merge.
+# @@ Does it make sense to split into separate files - one per redirect type?
+#
+
+: trace
+:
+{
+  $* <'cmd >!'  >'cmd >!'  : out
+  $* <'cmd 2>!' >'cmd 2>!' : err
+}
+
+: str
+:
+{
+  : literal
+  :
+  {
+    : portable-path
+    :
+    $* <<EOI >>EOO
+    cmd </foo >/bar 2>/baz
+    EOI
+    cmd </foo >/bar 2>/baz
+    EOO
+  }
+
+  : regex
+  :
+  {
+    : portable-path
+    :
+    $* <<EOI >>EOO
+    cmd >/~%foo% 2>/~%bar%
+    EOI
+    cmd >/~%foo% 2>/~%bar%
+    EOO
+  }
+}
+
+: doc
+:
+{
+  : literal
+  :
+  {
+    : portable-path
+    :
+    $* <<EOI >>EOO
+    cmd <</EOI_ >/EOO_ 2>/EOE_
+    foo
+    EOI_
+    bar
+    EOO_
+    baz
+    EOE_
+    EOI
+    cmd <</EOI_ >/EOO_ 2>/EOE_
+    foo
+    EOI_
+    bar
+    EOO_
+    baz
+    EOE_
+    EOO
+
+    : sharing
+    :
+    {
+      : in-out
+      :
+      $* <<EOI >>EOO
+      cmd <<:/EOF >>:/EOF
+      foo
+      EOF
+      EOI
+      cmd <<:/EOF >>:/EOF
+      foo
+      EOF
+      EOO
+
+      : different
+      :
+      {
+        : modifiers
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd <<:/EOF >>:EOF
+        foo
+        EOF
+        EOI
+        testscript:1:16: error: different modifiers for shared here-document 'EOF'
+        EOE
+
+        : quoting
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd <<EOF >>"EOF"
+        foo
+        EOF
+        EOI
+        testscript:1:13: error: different quoting for shared here-document 'EOF'
+        EOE
+      }
+    }
+  }
+
+  : regex
+  :
+  {
+    : portable-path
+    :
+    $* <<EOI >>EOO
+    cmd >/~%EOF% 2>/~%EOE%
+    foo
+    EOF
+    bar
+    EOE
+    EOI
+    cmd >/~%EOF% 2>/~%EOE%
+    foo
+    EOF
+    bar
+    EOE
+    EOO
+
+    : sharing
+    :
+    {
+      : in-out
+      :
+      $* <<EOI >>EOO
+      cmd >>~/EOF/ 2>>~/EOF/
+      foo
+      EOF
+      EOI
+      cmd >>~/EOF/ 2>>~/EOF/
+      foo
+      EOF
+      EOO
+
+      : different
+      :
+      {
+        : introducers
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd >>~/EOF/ 2>>~%EOF%
+        foo
+        EOF
+        EOI
+        testscript:1:18: error: different introducers for shared here-document regex 'EOF'
+        EOE
+
+        : flags
+        :
+        $* <<EOI 2>>EOE != 0
+        cmd >>~/EOF/ 2>>~/EOF/i
+        foo
+        EOF
+        EOI
+        testscript:1:18: error: different global flags for shared here-document regex 'EOF'
+        EOE
+      }
+    }
+  }
+}
+
+: file
+:
+{
+  : cmp
+  :
+  $* <<EOI >>EOO
+  cmd 0<<<a 1>>>b 2>>>c
+  EOI
+  cmd <<<a >>>b 2>>>c
+  EOO
+
+  : write
+  :
+  $* <<EOI >>EOO
+  cmd 1>=b 2>+c
+  EOI
+  cmd >=b 2>+c
+  EOO
+
+  : quote
+  :
+  $* <<EOI >>EOO
+  cmd 0<<<"a f" 1>="b f" 2>+"c f"
+  EOI
+  cmd <<<'a f' >='b f' 2>+'c f'
+  EOO
+
+  : in
+  :
+  {
+    : missed
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd <<<
+    EOI
+    testscript:1:8: error: missing stdin file
+    EOE
+
+    : empty
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd <<<""
+    EOI
+    testscript:1:8: error: empty stdin redirect path
+    EOE
+  }
+
+  : out
+  :
+  {
+    : missed
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd >=
+    EOI
+    testscript:1:7: error: missing stdout file
+    EOE
+
+    : empty
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd >=""
+    EOI
+    testscript:1:7: error: empty stdout redirect path
+    EOE
+  }
+
+  : err
+  :
+  {
+    : missed
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd 2>=
+    EOI
+    testscript:1:8: error: missing stderr file
+    EOE
+
+    : empty
+    :
+    $* <<EOI 2>>EOE !=0
+    cmd 2>=""
+    EOI
+    testscript:1:8: error: empty stderr redirect path
+    EOE
+  }
+}
+
+: merge
+{
+  : out
+  :
+  {
+    : err
+    :
+    $* <<EOI >>EOO
+    cmd 1>&2
+    EOI
+    cmd >&2
+    EOO
+
+    : no-mutual
+    :
+    $* <<EOI >>EOO
+    cmd 1>&2 2>&1 2>a
+    EOI
+    cmd >&2 2>a
+    EOO
+
+    : not-descriptor
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 1>&a
+    EOI
+    testscript:1:8: error: stdout merge redirect file descriptor must be 2
+    EOE
+
+    : self
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 1>&1
+    EOI
+    testscript:1:8: error: stdout merge redirect file descriptor must be 2
+    EOE
+
+    : missed
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 1>&
+    EOI
+    testscript:1:8: error: missing stdout file descriptor
+    EOE
+  }
+
+  : err
+  {
+    : out
+    :
+    $* <<EOI >>EOO
+    cmd 2>&1
+    EOI
+    cmd 2>&1
+    EOO
+
+    : no-mutual
+    :
+    $* <<EOI >>EOO
+    cmd 1>&2 2>&1 >a
+    EOI
+    cmd >a 2>&1
+    EOO
+
+    : not-descriptor
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 2>&a
+    EOI
+    testscript:1:8: error: stderr merge redirect file descriptor must be 1
+    EOE
+
+    : self
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 2>&2
+    EOI
+    testscript:1:8: error: stderr merge redirect file descriptor must be 1
+    EOE
+
+    : missed
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd 2>&
+    EOI
+    testscript:1:8: error: missing stderr file descriptor
+    EOE
+  }
+
+  : mutual
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd 1>&2 2>&1
+  EOI
+  testscript:1:14: error: stdout and stderr redirected to each other
+  EOE
+}
diff --git a/libbuild2/test/script/parser+regex.test.testscript b/libbuild2/test/script/parser+regex.test.testscript
new file mode 100644
index 0000000..d5f899a
--- /dev/null
+++ b/libbuild2/test/script/parser+regex.test.testscript
@@ -0,0 +1,223 @@
+# file      : libbuild2/test/script/parser+regex.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: here-string
+:
+{
+  : stdout
+  :
+  {
+    : missed
+    :
+    $* <'cmd >~' 2>>EOE != 0
+    testscript:1:7: error: missing stdout here-string regex
+    EOE
+
+    : no-introducer
+    :
+    $* <'cmd >~""' 2>>EOE != 0
+    testscript:1:7: error: no introducer character in stdout regex redirect
+    EOE
+
+    : no-term-introducer
+    :
+    $* <'cmd >~/' 2>>EOE != 0
+    testscript:1:7: error: no closing introducer character in stdout regex redirect
+    EOE
+
+    : portable-path-introducer
+    :
+    $* <'cmd >/~/foo/' 2>>EOE != 0
+    testscript:1:8: error: portable path modifier and '/' introducer in stdout regex redirect
+    EOE
+
+    : empty
+    :
+    $* <'cmd >~//' 2>>EOE != 0
+    testscript:1:7: error: stdout regex redirect is empty
+    EOE
+
+    : no-flags
+    :
+    $* <'cmd >~/fo*/' >'cmd >~/fo*/'
+
+    : idot
+    :
+    $* <'cmd >~/fo*/d' >'cmd >~/fo*/d'
+
+    : icase
+    :
+    $* <'cmd >~/fo*/i' >'cmd >~/fo*/i'
+
+    : invalid-flags1
+    :
+    $* <'cmd >~/foo/z' 2>>EOE != 0
+    testscript:1:7: error: junk at the end of stdout regex redirect
+    EOE
+
+    : invalid-flags2
+    :
+    $* <'cmd >~/foo/iz' 2>>EOE != 0
+    testscript:1:7: error: junk at the end of stdout regex redirect
+    EOE
+
+    : no-newline
+    :
+    $* <'cmd >:~/fo*/' >'cmd >:~/fo*/'
+  }
+
+  : stderr
+  :
+  {
+    : missed
+    :
+    $* <'cmd 2>~' 2>>EOE != 0
+    testscript:1:8: error: missing stderr here-string regex
+    EOE
+
+    : no-introducer
+    :
+    : Note that there is no need to reproduce all the errors as for stdout.
+    : All we need is to make sure that the proper description is passed to
+    : the parse_regex() function.
+    :
+    $* <'cmd 2>~""' 2>>EOE != 0
+    testscript:1:8: error: no introducer character in stderr regex redirect
+    EOE
+  }
+
+  : modifier-last
+  :
+  $* <'cmd >~/x' 2>>EOE != 0
+  testscript:1:7: error: no closing introducer character in stdout regex redirect
+  EOE
+}
+
+: here-doc
+:
+{
+  : stdout
+  :
+  {
+    : missed
+    :
+    $* <'cmd >>~' 2>>EOE != 0
+    testscript:1:8: error: expected here-document regex end marker
+    EOE
+
+    : portable-path-introducer
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd >>/~/EOO/
+    foo
+    EOO
+    EOI
+    testscript:1:5: error: portable path modifier and '/' introducer in here-document regex end marker
+    EOE
+
+    : unterminated-line-char
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd >>~/EOO/
+    /
+    EOO
+    EOI
+    testscript:2:1: error: no syntax line characters
+    EOE
+
+    : empty
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd >>:~/EOO/
+    EOO
+    EOI
+    testscript:2:1: error: empty here-document regex
+    EOE
+
+    : no-flags
+    :
+    $* <<EOI >>EOO
+    cmd 2>>~/EOE/
+    foo
+    /?
+    /foo/
+    /foo/*
+    /foo/i
+    /foo/i*
+
+    //
+    //*
+    EOE
+    EOI
+    cmd 2>>~/EOE/
+    foo
+    /?
+    /foo/
+    /foo/*
+    /foo/i
+    /foo/i*
+
+    //
+    //*
+    EOE
+    EOO
+
+    : no-newline
+    :
+    $* <'cmd >:~/fo*/' >'cmd >:~/fo*/'
+    $* <<EOI >>EOO
+    cmd 2>>:~/EOE/
+    foo
+    EOE
+    EOI
+    cmd 2>>:~/EOE/
+    foo
+    EOE
+    EOO
+
+    : end-marker-restore
+    :
+    {
+      : idot
+      :
+      $* <<EOI >>EOO
+      cmd 2>>~/EOE/d
+      foo
+      EOE
+      EOI
+      cmd 2>>~/EOE/d
+      foo
+      EOE
+      EOO
+
+      : icase
+      :
+      $* <<EOI >>EOO
+      cmd 2>>~/EOE/i
+      foo
+      EOE
+      EOI
+      cmd 2>>~/EOE/i
+      foo
+      EOE
+      EOO
+    }
+  }
+
+  : stderr
+  :
+  {
+    : missed
+    :
+    $* <'cmd 2>>~' 2>>EOE != 0
+    testscript:1:9: error: expected here-document regex end marker
+    EOE
+  }
+
+  : modifier-last
+  :
+  $* <'cmd >>~:/FOO/' 2>>EOE != 0
+  testscript:1:8: error: expected here-document regex end marker
+  EOE
+}
diff --git a/libbuild2/test/script/parser+scope-if.test.testscript b/libbuild2/test/script/parser+scope-if.test.testscript
new file mode 100644
index 0000000..aad3f37
--- /dev/null
+++ b/libbuild2/test/script/parser+scope-if.test.testscript
@@ -0,0 +1,554 @@
+# file      : libbuild2/test/script/parser+scope-if.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: if
+:
+{
+  : true
+  :
+  $* -s <<EOI >>EOO
+  if true foo
+  {
+    cmd
+  }
+  EOI
+  {
+    ? true foo
+    {
+      cmd
+    }
+  }
+  EOO
+
+  : false
+  :
+  $* -s <<EOI >>EOO
+  if false foo
+  {
+    cmd
+  }
+  EOI
+  {
+    ? false foo
+  }
+  EOO
+
+  : not-true
+  :
+  $* -s <<EOI >>EOO
+  if! true
+  {
+    cmd
+  }
+  EOI
+  {
+    ? true
+  }
+  EOO
+
+  : not-false
+  :
+  $* -s <<EOI >>EOO
+  if! false
+  {
+    cmd
+  }
+  EOI
+  {
+    ? false
+    {
+      cmd
+    }
+  }
+  EOO
+
+  : eos-inside
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+  {
+  EOI
+  testscript:3:1: error: expected '}' at the end of the scope
+  EOE
+
+}
+
+: elif
+:
+{
+  : true
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd
+  }
+  elif true
+  {
+    cmd1
+  }
+  EOI
+  {
+    ? false
+    ? true
+    {
+      cmd1
+    }
+  }
+  EOO
+
+  : false
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd
+  }
+  elif false
+  {
+    cmd
+  }
+  EOI
+  {
+    ? false
+    ? false
+  }
+  EOO
+
+  : not-false
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd
+  }
+  elif! false
+  {
+    cmd1
+  }
+  EOI
+  {
+    ? false
+    ? false
+    {
+      cmd1
+    }
+  }
+  EOO
+
+  : not-true
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd
+  }
+  elif! true
+  {
+    cmd
+  }
+  EOI
+  {
+    ? false
+    ? true
+  }
+  EOO
+
+  : after-else
+  :
+  $* <<EOI 2>>EOE != 0
+  if false
+  {
+    cmd
+  }
+  else
+  {
+    cmd
+  }
+  elif true
+  {
+    cmd
+  }
+  EOI
+  testscript:9:1: error: 'elif' after 'else'
+  EOE
+}
+
+: else
+:
+{
+  : true
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd
+  }
+  else
+  {
+    cmd1
+  }
+  EOI
+  {
+    ? false
+    {
+      cmd1
+    }
+  }
+  EOO
+
+  : false
+  :
+  $* -s <<EOI >>EOO
+  if true
+  {
+    cmd1
+  }
+  else
+  {
+    cmd
+  }
+  EOI
+  {
+    ? true
+    {
+      cmd1
+    }
+  }
+  EOO
+
+  : chain
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd
+  }
+  elif false
+  {
+    cmd
+    cmd
+  }
+  elif false
+  {
+    cmd
+  }
+  elif true
+  {
+    cmd1
+    cmd2
+  }
+  elif false
+  {
+    cmd
+  }
+  else
+  {
+    cmd
+    cmd
+  }
+  EOI
+  {
+    ? false
+    ? false
+    ? false
+    ? true
+    {
+      {
+        cmd1
+      }
+      {
+        cmd2
+      }
+    }
+  }
+  EOO
+
+  : scope-expected
+  :
+  $* <<EOI 2>>EOE != 0
+  if
+  {
+    cmd
+  }
+  else
+  cmd
+  EOI
+  testscript:5:1: error: expected scope after 'else'
+  EOE
+
+  : after-else
+  :
+  $* <<EOI 2>>EOE != 0
+  if false
+  {
+    cmd
+  }
+  else
+  {
+    cmd
+  }
+  else
+  {
+    cmd
+  }
+  EOI
+  testscript:9:1: error: 'else' after 'else'
+  EOE
+}
+
+: nested
+:
+{
+  : take
+  :
+  $* -s <<EOI >>EOO
+  if true
+  {
+    cmd1
+    if false
+    {
+      cmd
+    }
+    elif false
+    {
+      if true
+      {
+        cmd
+      }
+    }
+    else
+    {
+      cmd2
+    }
+    cmd3
+  }
+  EOI
+  {
+    ? true
+    {
+      {
+        cmd1
+      }
+      ? false
+      ? false
+      {
+        {
+          cmd2
+        }
+      }
+      {
+        cmd3
+      }
+    }
+  }
+  EOO
+
+  : skip
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd1
+    if false
+    {
+      cmd
+    }
+    elif false
+    {
+      if true
+      {
+        cmd
+      }
+    }
+    else
+    {
+      cmd2
+    }
+    cmd3
+  }
+  else
+  {
+    cmd
+  }
+  EOI
+  {
+    ? false
+    {
+      {
+        cmd
+      }
+    }
+  }
+  EOO
+}
+
+: demote
+:
+{
+  : group
+  : Chain remains a group
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd
+  }
+  elif true
+  {
+    cmd1
+    cmd2
+  }
+  else
+  {
+    cmd
+  }
+  EOI
+  {
+    ? false
+    ? true
+    {
+      {
+        cmd1
+      }
+      {
+        cmd2
+      }
+    }
+  }
+  EOO
+
+  : test
+  : Chain demoted to test
+  :
+  $* -s <<EOI >>EOO
+  if false
+  {
+    cmd
+  }
+  elif true
+  {
+    cmd1
+  }
+  else
+  {
+    cmd
+  }
+  EOI
+  {
+    ? false
+    ? true
+    {
+      cmd1
+    }
+  }
+  EOO
+}
+
+: line-index
+: Make sure command line index spans setup/if/teardown
+:
+$* -s -l <<EOI >>EOO
++setup          # 1
+
+if false one    # 2
+{
+  cmd
+}
+elif false two  # 3
+{
+  cmd
+}
+elif true       # 4
+{
+  cmd1
+}
+elif false      # 5
+{
+  cmd
+}
+else
+{
+  cmd
+}
+
+if false one    # 6
+{
+  cmd
+}
+elif false two  # 7
+{
+  cmd
+}
+else
+{
+  cmd2
+}
+
+-tdown          # 8
+EOI
+{
+  +setup # 1
+  ? false one # 2
+  ? false two # 3
+  ? true # 4
+  {
+    cmd1 # 0
+  }
+  ? false one # 6
+  ? false two # 7
+  {
+    cmd2 # 0
+  }
+  -tdown # 8
+}
+EOO
+
+: scope-comman-if
+:
+$* -s <<EOI >>EOO
+if true
+{
+  cmd
+}
+if true
+  cmd1
+  cmd2
+end
+EOI
+{
+  ? true
+  {
+    cmd
+  }
+  {
+    ? true
+    cmd1
+    cmd2
+  }
+}
+EOO
+
+: shared-id-desc
+:
+$* -s -i <<EOI >>EOO
+: test summary
+:
+if false
+{
+  cmd
+}
+else
+{
+  cmd1
+}
+EOI
+{
+  ? false
+  : sm:test summary
+  { # 3
+    cmd1
+  }
+}
+EOO
diff --git a/libbuild2/test/script/parser+scope.test.testscript b/libbuild2/test/script/parser+scope.test.testscript
new file mode 100644
index 0000000..bfb1a59
--- /dev/null
+++ b/libbuild2/test/script/parser+scope.test.testscript
@@ -0,0 +1,280 @@
+# file      : libbuild2/test/script/parser+scope.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+$* testscript     <'cmd $@' >"cmd 1"     : id-testscript
+$* foo.testscript <'cmd $@' >"cmd foo/1" : id
+
+: wd-testscript
+:
+$* testscript <'cmd "$~"' >~"%cmd '?.+[/\\\\]test-driver[/\\\\]1'?%"
+
+: wd
+:
+$* foo.testscript <'cmd "$~"' >~"%cmd '?.+[/\\\\]test-driver[/\\\\]foo[/\\\\]1'?%"
+
+: group
+:
+{
+  : empty
+  :
+  $* -s <<EOI
+  {
+  }
+  EOI
+
+  : empty-empty
+  :
+  $* -s <<EOI
+  {
+    {
+    }
+  }
+  EOI
+
+  : non-empty
+  :
+  $* -s <<EOI >>EOO
+  {
+    cmd1
+    cmd2
+  }
+  EOI
+  {
+    {
+      {
+        cmd1
+      }
+      {
+        cmd2
+      }
+    }
+  }
+  EOO
+}
+
+: test
+:
+{
+  : explicit
+  :
+  {
+    : one-level
+    :
+    $* -s -i <<EOI >>EOO
+    {
+      cmd
+    }
+    EOI
+    {
+      { # 1
+        cmd
+      }
+    }
+    EOO
+
+    : nested
+    :
+    $* -s -i <<EOI >>EOO
+    {
+      {
+        cmd
+      }
+    }
+    EOI
+    {
+      { # 1
+        cmd
+      }
+    }
+    EOO
+
+    : var
+    :
+    $* -s -i <<EOI >>EOO
+    {
+      x = abc
+      cmd $x
+    }
+    EOI
+    {
+      { # 1
+        cmd abc
+      }
+    }
+    EOO
+
+    : setup
+    :
+    $* -s -i <<EOI >>EOO
+    {
+      x = abc
+      +setup
+      cmd $x
+    }
+    EOI
+    {
+      { # 1
+        +setup
+        { # 1/4
+          cmd abc
+        }
+      }
+    }
+    EOO
+  }
+
+  : implicit
+  {
+    : one-cmd
+    :
+    $* -s <<EOI >>EOO
+    cmd1
+    EOI
+    {
+      {
+        cmd1
+      }
+    }
+    EOO
+
+    : two-cmd
+    :
+    $* -s <<EOI >>EOO
+    cmd1;
+    cmd2
+    EOI
+    {
+      {
+        cmd1
+        cmd2
+      }
+    }
+    EOO
+
+    : three-cmd
+    :
+    $* -s <<EOI >>EOO
+    cmd1;
+    cmd2;
+    cmd3
+    EOI
+    {
+      {
+        cmd1
+        cmd2
+        cmd3
+      }
+    }
+    EOO
+
+    : var
+    :
+    $* -s <<EOI >>EOO
+    cmd1;
+    x = abc;
+    cmd2 $x
+    EOI
+    {
+      {
+        cmd1
+        cmd2 abc
+      }
+    }
+    EOO
+
+    : var-first
+    :
+    $* -s <<EOI >>EOO
+    x = abc;
+    cmd $x
+    EOI
+    {
+      {
+        cmd abc
+      }
+    }
+    EOO
+
+    : var-setup-tdown
+    :
+    $* -s <<EOI >>EOO
+    x = abc
+    cmd $x
+    y = 123
+    EOI
+    {
+      {
+        cmd abc
+      }
+    }
+    EOO
+
+    : after-tdown
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd1
+    x = abc
+    cmd2
+    EOI
+    testscript:3:1: error: test after teardown
+      testscript:2:1: info: last teardown line appears here
+    EOE
+  }
+}
+
+: expected
+{
+  : newline-lcbrace
+  :
+  $* <:"{x" 2>>EOE != 0
+  testscript:1:2: error: expected newline after '{'
+  EOE
+
+  : rcbrace
+  :
+  $* <"{" 2>>EOE != 0
+  testscript:2:1: error: expected '}' at the end of the scope
+  EOE
+
+  : line-rcbrace
+  :
+  $* <<EOI 2>>EOE != 0
+  {
+    cmd;
+  }
+  EOI
+  testscript:3:1: error: expected another line after ';'
+  EOE
+
+  : newline-rcbrace
+  :
+  $* <<:EOI 2>>EOE != 0
+  {
+  }
+  EOI
+  testscript:2:2: error: expected newline after '}'
+  EOE
+
+  : line-eof
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd;
+  EOI
+  testscript:2:1: error: expected another line after ';'
+  EOE
+
+  : newline-cmd
+  :
+  $* <<:EOI 2>>EOE != 0
+  cmd;
+  EOI
+  testscript:1:5: error: expected newline instead of <end of file>
+  EOE
+
+  : newline-var
+  :
+  $* <:"x = abc;" 2>>EOE != 0
+  testscript:1:9: error: expected newline instead of <end of file>
+  EOE
+}
diff --git a/libbuild2/test/script/parser+setup-teardown.test.testscript b/libbuild2/test/script/parser+setup-teardown.test.testscript
new file mode 100644
index 0000000..5f1418a
--- /dev/null
+++ b/libbuild2/test/script/parser+setup-teardown.test.testscript
@@ -0,0 +1,151 @@
+# file      : libbuild2/test/script/parser+setup-teardown.test.testscript
+# copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+# license   : MIT; see accompanying LICENSE file
+
+: setup
+:
+{
+  : followed
+  :
+  {
+    : semi
+    :
+    $* <"+cmd;" 2>>EOE != 0
+    testscript:1:5: error: ';' after setup command
+    EOE
+
+    : colon
+    :
+    $* <"+cmd:" 2>>EOE != 0
+    testscript:1:5: error: ':' after setup command
+    EOE
+  }
+
+  : after
+  :
+  {
+    : test
+    :
+    $* <<EOI 2>>EOE != 0
+    cmd
+    +cmd
+    EOI
+    testscript:2:1: error: setup command after tests
+    EOE
+
+    : after-tdownt
+    :
+    $* <<EOI 2>>EOE != 0
+    -cmd
+    +cmd
+    EOI
+    testscript:2:1: error: setup command after teardown
+    EOE
+  }
+
+  : in-test
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd;
+  +cmd
+  EOI
+  testscript:2:1: error: setup command in test
+  EOE
+}
+
+: tdown
+:
+{
+  : followed
+  :
+  {
+    : semi
+    :
+    $* <"-cmd;" 2>>EOE != 0
+    testscript:1:5: error: ';' after teardown command
+    EOE
+
+    : colon
+    :
+    $* <"-cmd:" 2>>EOE != 0
+    testscript:1:5: error: ':' after teardown command
+    EOE
+  }
+
+  : in-test
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd;
+  -cmd
+  EOI
+  testscript:2:1: error: teardown command in test
+  EOE
+}
+
+: var
+:
+{
+  : between-tests
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  x = y
+  cmd
+  EOI
+  testscript:3:1: error: test after teardown
+    testscript:2:1: info: last teardown line appears here
+  EOE
+
+  : between-tests-scope
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  x = y
+  {
+    cmd
+  }
+  EOI
+  testscript:3:1: error: scope after teardown
+    testscript:2:1: info: last teardown line appears here
+  EOE
+
+  : between-tests-command-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  x = y
+  if true
+    cmd
+  end
+  EOI
+  testscript:3:1: error: test after teardown
+    testscript:2:1: info: last teardown line appears here
+  EOE
+
+  : between-tests-scope-if
+  :
+  $* <<EOI 2>>EOE != 0
+  cmd
+  x = y
+  if true
+  {
+    cmd
+  }
+  EOI
+  testscript:3:1: error: scope after teardown
+    testscript:2:1: info: last teardown line appears here
+  EOE
+
+  : between-tests-variable-if
+  :
+  $* <<EOI >>EOO
+  cmd
+  x = y
+  if true
+    y = x
+  end
+  EOI
+  cmd
+  ? true
+  EOO
+}
diff --git a/libbuild2/test/script/parser.cxx b/libbuild2/test/script/parser.cxx
new file mode 100644
index 0000000..260bc88
--- /dev/null
+++ b/libbuild2/test/script/parser.cxx
@@ -0,0 +1,3451 @@
+// file      : libbuild2/test/script/parser.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/test/script/parser.hxx>
+
+#include <sstream>
+
+#include <libbuild2/context.hxx> // sched, keep_going
+
+#include <libbuild2/test/script/lexer.hxx>
+#include <libbuild2/test/script/runner.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      using type = token_type;
+
+      // Return true if the string contains only a single digit characters
+      // (used to detect the special $N variables).
+      //
+      static inline bool
+      digit (const string& s)
+      {
+        return s.size () == 1 && butl::digit (s[0]);
+      }
+
+      //
+      // Pre-parse.
+      //
+
+      void parser::
+      pre_parse (script& s)
+      {
+        const path& p (s.script_target.path ());
+        assert (!p.empty ()); // Should have been assigned.
+
+        try
+        {
+          ifdstream ifs (p);
+          pre_parse (ifs, s);
+        }
+        catch (const io_error& e)
+        {
+          fail << "unable to read testscript " << p << ": " << e << endf;
+        }
+      }
+
+      void parser::
+      pre_parse (istream& is, script& s)
+      {
+        path_ = &*s.paths_.insert (s.script_target.path ()).first;
+
+        pre_parse_ = true;
+
+        lexer l (is, *path_, lexer_mode::command_line);
+        set_lexer (&l);
+
+        id_prefix_.clear ();
+
+        id_map idm;
+        include_set ins;
+
+        script_ = &s;
+        runner_ = nullptr;
+        group_ = script_;
+        id_map_ = &idm;
+        include_set_ = &ins;
+        scope_ = nullptr;
+
+        //@@ PAT TODO: set pbase_?
+
+        // Start location of the implied script group is the beginning of
+        // the file. End location -- end of the file.
+        //
+        group_->start_loc_ = location (path_, 1, 1);
+
+        token t (pre_parse_scope_body ());
+
+        if (t.type != type::eos)
+          fail (t) << "stray " << t;
+
+        group_->end_loc_ = get_location (t);
+      }
+
+      bool parser::
+      pre_parse_demote_group_scope (unique_ptr<scope>& s)
+      {
+        // See if this turned out to be an explicit test scope. An explicit
+        // test scope contains a single test, only variable assignments in
+        // setup and nothing in teardown. Plus only the group can have the
+        // description. Because we apply this recursively, also disqualify
+        // a test scope that has an if-condition.
+        //
+        // If we have a chain, then all the scopes must be demotable. So we
+        // first check if this scope is demotable and if so then recurse for
+        // the next in chain.
+        //
+        group& g (static_cast<group&> (*s));
+
+        auto& sc (g.scopes);
+        auto& su (g.setup_);
+        auto& td (g.tdown_);
+
+        test* t;
+        if (sc.size () == 1                                          &&
+            (t = dynamic_cast<test*> (sc.back ().get ())) != nullptr &&
+            find_if (
+              su.begin (), su.end (),
+              [] (const line& l) {
+                return l.type != line_type::var;
+              }) == su.end ()                                        &&
+
+            td.empty ()                                              &&
+            !t->desc                                                 &&
+            !t->if_cond_)
+        {
+          if (g.if_chain != nullptr &&
+              !pre_parse_demote_group_scope (g.if_chain))
+            return false;
+
+          // It would have been nice to reuse the test object and only throw
+          // away the group. However, the merged scope has to use id_path and
+          // wd_path of the group. So to keep things simple we are going to
+          // throw away both and create a new test object.
+          //
+          // We always use the group's id since the test cannot have a
+          // user-provided one.
+          //
+          unique_ptr<test> m (new test (g.id_path.leaf ().string (), *group_));
+
+          // Move the description, if-condition, and if-chain.
+          //
+          m->desc = move (g.desc);
+          m->if_cond_ = move (g.if_cond_);
+          m->if_chain = move (g.if_chain);
+
+          // Merge the lines of the group and the test.
+          //
+          if (su.empty ())
+            m->tests_ = move (t->tests_);
+          else
+          {
+            m->tests_ = move (su); // Should come first.
+            m->tests_.insert (m->tests_.end (),
+                              make_move_iterator (t->tests_.begin ()),
+                              make_move_iterator (t->tests_.end ()));
+          }
+
+          // Use start/end locations of the outer scope.
+          //
+          m->start_loc_ = g.start_loc_;
+          m->end_loc_ = g.end_loc_;
+
+          s = move (m);
+          return true;
+        }
+
+        return false;
+      }
+
+      token parser::
+      pre_parse_scope_body ()
+      {
+        // enter: next token is first token of scope body
+        // leave: rcbrace or eos (returned)
+
+        token t;
+        type tt;
+
+        // Parse lines (including nested scopes) until we see '}' or eos.
+        //
+        for (;;)
+        {
+          // Start lexing each line recognizing leading '.+-{}'.
+          //
+          tt = peek (lexer_mode::first_token);
+
+          // Handle description.
+          //
+          optional<description> d;
+          if (tt == type::colon)
+            d = pre_parse_leading_description (t, tt);
+
+          // Determine the line type by peeking at the first token.
+          //
+          switch (tt)
+          {
+          case type::eos:
+          case type::rcbrace:
+            {
+              next (t, tt);
+
+              if (d)
+                fail (t) << "description before " << t;
+
+              return t;
+            }
+          case type::lcbrace:
+            {
+              // Nested scope.
+              //
+              next (t, tt); // Get '{'.
+              const location sl (get_location (t));
+
+              // First check that we don't have any teardown commands yet.
+              // This will detect things like variable assignments between
+              // scopes.
+              //
+              if (!group_->tdown_.empty ())
+              {
+                location tl (
+                  group_->tdown_.back ().tokens.front ().location ());
+
+                fail (sl) << "scope after teardown" <<
+                  info (tl) << "last teardown line appears here";
+              }
+
+              // If there is no user-supplied id, use the line number
+              // (prefixed with include id) as the scope id.
+              //
+              const string& id (
+                d && !d->id.empty ()
+                ? d->id
+                : insert_id (id_prefix_ + to_string (sl.line), sl));
+
+              unique_ptr<scope> g (pre_parse_scope_block (t, tt, id));
+              g->desc = move (d);
+
+              pre_parse_demote_group_scope (g);
+              group_->scopes.push_back (move (g));
+              continue;
+            }
+          default:
+            {
+              pre_parse_line (t, tt, d);
+              assert (tt == type::newline);
+              break;
+            }
+          }
+        }
+      }
+
+      unique_ptr<group> parser::
+      pre_parse_scope_block (token& t, type& tt, const string& id)
+      {
+        // enter: lcbrace
+        // leave: newline after rcbrace
+
+        const location sl (get_location (t));
+
+        if (next (t, tt) != type::newline)
+          fail (t) << "expected newline after '{'";
+
+        // Push group.
+        //
+        id_map idm;
+        include_set ins;
+
+        unique_ptr<group> g (new group (id, *group_));
+
+        id_map* om (id_map_);
+        id_map_ = &idm;
+
+        include_set* os (include_set_);
+        include_set_ = &ins;
+
+        group* og (group_);
+        group_ = g.get ();
+
+        // Parse body.
+        //
+        group_->start_loc_ = sl;
+        token e (pre_parse_scope_body ());
+        group_->end_loc_ = get_location (e);
+
+        // Pop group.
+        //
+        group_ = og;
+        include_set_ = os;
+        id_map_ = om;
+
+        if (e.type != type::rcbrace)
+          fail (e) << "expected '}' at the end of the scope";
+
+        if (next (t, tt) != type::newline)
+          fail (t) << "expected newline after '}'";
+
+        return g;
+      }
+
+      // Parse a logical line (as well as scope-if since the only way to
+      // recognize it is to parse the if line).
+      //
+      // If one is true then only parse one line returning an indication of
+      // whether the line ended with a semicolon.
+      //
+      bool parser::
+      pre_parse_line (token& t, type& tt,
+                      optional<description>& d,
+                      lines* ls,
+                      bool one)
+      {
+        // enter: next token is peeked at (type in tt)
+        // leave: newline
+
+        // Note: token is only peeked at.
+        //
+        const location ll (get_location (peeked ()));
+
+        // Determine the line type/start token.
+        //
+        line_type lt;
+        type st (type::eos);
+
+        switch (tt)
+        {
+        case type::dot:
+          {
+            // Directive.
+            //
+            next (t, tt); // Skip dot.
+            next (t, tt); // Get the directive name.
+
+            if (tt != type::word || t.qtype != quote_type::unquoted)
+              fail (t) << "expected directive name instead of " << t;
+
+            // Make sure we are not inside a test (i.e., after semi).
+            //
+            if (ls != nullptr)
+              fail (ll) << "directive after ';'";
+
+            const string& n (t.value);
+
+            if (n == "include")
+              pre_parse_directive (t, tt);
+            else
+              fail (t) << "unknown directive '" << n << "'";
+
+            assert (tt == type::newline);
+            return false;
+          }
+        case type::plus:
+        case type::minus:
+          {
+            // Setup/teardown command.
+            //
+            st = tt;
+
+            next (t, tt);   // Start saving tokens from the next one.
+            replay_save ();
+            next (t, tt);
+
+            // See if this is a special command.
+            //
+            lt = line_type::cmd; // Default.
+
+            if (tt == type::word && t.qtype == quote_type::unquoted)
+            {
+              const string& n (t.value);
+
+              if      (n == "if")  lt = line_type::cmd_if;
+              else if (n == "if!") lt = line_type::cmd_ifn;
+            }
+
+            break;
+          }
+        default:
+          {
+            // Either variable assignment or test command.
+            //
+            replay_save (); // Start saving tokens from the current one.
+            next (t, tt);
+
+            // Decide whether this is a variable assignment or a command.
+            //
+            // It is an assignment if the first token is an unquoted name and
+            // the next token is an assign/append/prepend operator. Assignment
+            // to a computed variable name must use the set builtin.
+            //
+            // Note also thatspecial commands take precedence over variable
+            // assignments.
+            //
+            lt = line_type::cmd; // Default.
+
+            if (tt == type::word && t.qtype == quote_type::unquoted)
+            {
+              const string& n (t.value);
+
+              if      (n == "if")    lt = line_type::cmd_if;
+              else if (n == "if!")   lt = line_type::cmd_ifn;
+              else if (n == "elif")  lt = line_type::cmd_elif;
+              else if (n == "elif!") lt = line_type::cmd_elifn;
+              else if (n == "else")  lt = line_type::cmd_else;
+              else if (n == "end")   lt = line_type::cmd_end;
+              else
+              {
+                // Switch the recognition of leading variable assignments for
+                // the next token. This is safe to do because we know we
+                // cannot be in the quoted mode (since the current token is
+                // not quoted).
+                //
+                type p (peek (lexer_mode::second_token));
+
+                if (p == type::assign  ||
+                    p == type::prepend ||
+                    p == type::append)
+                {
+                  lt = line_type::var;
+                  st = p;
+                }
+              }
+            }
+
+            break;
+          }
+        }
+
+        // Pre-parse the line keeping track of whether it ends with a semi.
+        //
+        bool semi (false);
+
+        line ln;
+        switch (lt)
+        {
+        case line_type::var:
+          {
+            // Check if we are trying to modify any of the special aliases
+            // ($*, $N, $~, $@).
+            //
+            string& n (t.value);
+
+            if (n == "*" || n == "~" || n == "@" || digit (n))
+              fail (t) << "attempt to set '" << n << "' variable directly";
+
+            // Pre-enter the variables now while we are executing serially.
+            // Once parallel, it becomes a lot harder to do.
+            //
+            ln.var = &script_->var_pool.insert (move (n));
+
+            next (t, tt); // Assignment kind.
+            parse_variable_line (t, tt);
+
+            semi = (tt == type::semi);
+
+            if (tt == type::semi)
+              next (t, tt);
+
+            if (tt != type::newline)
+              fail (t) << "expected newline instead of " << t;
+
+            break;
+          }
+        case line_type::cmd_if:
+        case line_type::cmd_ifn:
+        case line_type::cmd_elif:
+        case line_type::cmd_elifn:
+        case line_type::cmd_else:
+        case line_type::cmd_end:
+          next (t, tt); // Skip to start of command.
+          // Fall through.
+        case line_type::cmd:
+          {
+            pair<command_expr, here_docs> p;
+
+            if (lt != line_type::cmd_else && lt != line_type::cmd_end)
+              p = parse_command_expr (t, tt);
+
+            // Colon and semicolon are only valid in test command lines and
+            // after 'end' in if-else. Note that we still recognize them
+            // lexically, they are just not valid tokens per the grammar.
+            //
+            if (tt != type::newline)
+            {
+              if (lt != line_type::cmd && lt != line_type::cmd_end)
+                fail (t) << "expected newline instead of " << t;
+
+              switch (st)
+              {
+              case type::plus:  fail (t) << t << " after setup command" << endf;
+              case type::minus: fail (t) << t << " after teardown command" << endf;
+              }
+            }
+
+            switch (tt)
+            {
+            case type::colon:
+              {
+                if (d)
+                  fail (ll) << "both leading and trailing descriptions";
+
+                d = parse_trailing_description (t, tt);
+                break;
+              }
+            case type::semi:
+              {
+                semi = true;
+                next (t, tt); // Get newline.
+                break;
+              }
+            }
+
+            if (tt != type::newline)
+              fail (t) << "expected newline instead of " << t;
+
+            parse_here_documents (t, tt, p);
+            break;
+          }
+        }
+
+        assert (tt == type::newline);
+
+        // Stop saving and get the tokens.
+        //
+        lines ls_data;
+
+        if (ls == nullptr)
+          ls = &ls_data;
+
+        ln.type = lt;
+        ln.tokens = replay_data ();
+        ls->push_back (move (ln));
+
+        if (lt == line_type::cmd_if || lt == line_type::cmd_ifn)
+        {
+          semi = pre_parse_if_else (t, tt, d, *ls);
+
+          // If this turned out to be scope-if, then ls is empty, semi is
+          // false, and none of the below logic applies.
+          //
+          if (ls->empty ())
+            return semi;
+        }
+
+        // Unless we were told where to put it, decide where it actually goes.
+        //
+        if (ls == &ls_data)
+        {
+          // First pre-check variable and variable-if: by themselves (i.e.,
+          // without a trailing semicolon) they are treated as either setup or
+          // teardown without plus/minus. Also handle illegal line types.
+          //
+          switch (lt)
+          {
+          case line_type::cmd_elif:
+          case line_type::cmd_elifn:
+          case line_type::cmd_else:
+          case line_type::cmd_end:
+            {
+              fail (ll) << lt << " without preceding 'if'" << endf;
+            }
+          case line_type::cmd_if:
+          case line_type::cmd_ifn:
+            {
+              // See if this is a variable-only command-if.
+              //
+              if (find_if (ls_data.begin (), ls_data.end (),
+                           [] (const line& l) {
+                             return l.type == line_type::cmd;
+                           }) != ls_data.end ())
+                break;
+            }
+            // Fall through.
+          case line_type::var:
+            {
+              // If there is a semicolon after the variable then we assume
+              // it is part of a test (there is no reason to use semicolons
+              // after variables in the group scope). Otherwise -- setup or
+              // teardown.
+              //
+              if (!semi)
+              {
+                if (d)
+                {
+                  if (lt == line_type::var)
+                    fail (ll) << "description before setup/teardown variable";
+                  else
+                    fail (ll) << "description before/after setup/teardown "
+                              << "variable-if";
+                }
+
+                // If we don't have any nested scopes or teardown commands,
+                // then we assume this is a setup, otherwise -- teardown.
+                //
+                ls = group_->scopes.empty () && group_->tdown_.empty ()
+                  ? &group_->setup_
+                  : &group_->tdown_;
+              }
+              break;
+            }
+          default:
+            break;
+          }
+
+          // If pre-check didn't change the destination, then it's a test.
+          //
+          if (ls == &ls_data)
+          {
+            switch (st)
+            {
+              // Setup.
+              //
+            case type::plus:
+              {
+                if (d)
+                  fail (ll) << "description before setup command";
+
+                if (!group_->scopes.empty ())
+                  fail (ll) << "setup command after tests";
+
+                if (!group_->tdown_.empty ())
+                  fail (ll) << "setup command after teardown";
+
+                ls = &group_->setup_;
+                break;
+              }
+
+              // Teardown.
+              //
+            case type::minus:
+              {
+                if (d)
+                  fail (ll) << "description before teardown command";
+
+                ls = &group_->tdown_;
+                break;
+              }
+
+              // Test command or variable.
+              //
+            default:
+              {
+                // First check that we don't have any teardown commands yet.
+                // This will detect things like variable assignments between
+                // tests.
+                //
+                if (!group_->tdown_.empty ())
+                {
+                  location tl (
+                    group_->tdown_.back ().tokens.front ().location ());
+
+                  fail (ll) << "test after teardown" <<
+                    info (tl) << "last teardown line appears here";
+                }
+                break;
+              }
+            }
+          }
+
+          // If the destination changed, then move the data over.
+          //
+          if (ls != &ls_data)
+            ls->insert (ls->end (),
+                        make_move_iterator (ls_data.begin ()),
+                        make_move_iterator (ls_data.end ()));
+        }
+
+        // If this command ended with a semicolon, then the next one should
+        // go to the same place.
+        //
+        if (semi && !one)
+        {
+          tt = peek (lexer_mode::first_token);
+          const location ll (get_location (peeked ()));
+
+          switch (tt)
+          {
+          case type::colon:
+            fail (ll) << "description inside test" << endf;
+          case type::eos:
+          case type::rcbrace:
+          case type::lcbrace:
+            fail (ll) << "expected another line after ';'" << endf;
+          case type::plus:
+            fail (ll) << "setup command in test" << endf;
+          case type::minus:
+            fail (ll) << "teardown command in test" << endf;
+          default:
+            semi = pre_parse_line (t, tt, d, ls);
+            assert (tt == type::newline); // End of last test line.
+          }
+        }
+
+        // If this is a test then create implicit test scope.
+        //
+        if (ls == &ls_data)
+        {
+          // If there is no user-supplied id, use the line number (prefixed
+          // with include id) as the scope id.
+          //
+          const string& id (
+            d && !d->id.empty ()
+            ? d->id
+            : insert_id (id_prefix_ + to_string (ll.line), ll));
+
+          unique_ptr<test> p (new test (id, *group_));
+
+          p->desc = move (d);
+
+          p->start_loc_ = ll;
+          p->tests_ = move (ls_data);
+          p->end_loc_ = get_location (t);
+
+          group_->scopes.push_back (move (p));
+        }
+
+        return semi;
+      }
+
+      bool parser::
+      pre_parse_if_else (token& t, type& tt,
+                         optional<description>& d,
+                         lines& ls)
+      {
+        // enter: <newline> (previous line)
+        // leave: <newline>
+
+        tt = peek (lexer_mode::first_token);
+
+        return tt == type::lcbrace
+          ? pre_parse_if_else_scope (t, tt, d, ls)
+          : pre_parse_if_else_command (t, tt, d, ls);
+      }
+
+      bool parser::
+      pre_parse_if_else_scope (token& t, type& tt,
+                               optional<description>& d,
+                               lines& ls)
+      {
+        // enter: peeked token of next line (lcbrace)
+        // leave: newline
+
+        assert (ls.size () == 1); // The if/if! line.
+
+        // Use if/if! as the entire scope chain location.
+        //
+        const location sl (ls.back ().tokens.front ().location ());
+
+        // First check that we don't have any teardown commands yet. This
+        // will detect things like variable assignments between scopes.
+        //
+        if (!group_->tdown_.empty ())
+        {
+          location tl (
+            group_->tdown_.back ().tokens.front ().location ());
+
+          fail (sl) << "scope after teardown" <<
+            info (tl) << "last teardown line appears here";
+        }
+
+        // If there is no user-supplied id, use the line number (prefixed with
+        // include id) as the scope id. Note that we use the same id for all
+        // scopes in the chain.
+        //
+        const string& id (
+          d && !d->id.empty ()
+          ? d->id
+          : insert_id (id_prefix_ + to_string (sl.line), sl));
+
+        unique_ptr<scope> root;
+
+        // Parse the if-else scope chain.
+        //
+        line_type bt (line_type::cmd_if); // Current block.
+
+        for (unique_ptr<scope>* ps (&root);; ps = &(*ps)->if_chain)
+        {
+          next (t, tt); // Get '{'.
+
+          {
+            unique_ptr<group> g (pre_parse_scope_block (t, tt, id));
+
+            // If-condition.
+            //
+            g->if_cond_ = move (ls.back ());
+            ls.clear ();
+
+            // Description. For now we just duplicate it through the entire
+            // chain.
+            //
+            g->desc = (ps == &root ? d : root->desc);
+
+            *ps = move (g);
+          }
+
+          // See if what comes next is another chain element.
+          //
+          line_type lt (line_type::cmd_end);
+
+          type pt (peek (lexer_mode::first_token));
+          const token& p (peeked ());
+          const location ll (get_location (p));
+
+          if (pt == type::word && p.qtype == quote_type::unquoted)
+          {
+            if      (p.value == "elif")  lt = line_type::cmd_elif;
+            else if (p.value == "elif!") lt = line_type::cmd_elifn;
+            else if (p.value == "else")  lt = line_type::cmd_else;
+          }
+
+          if (lt == line_type::cmd_end)
+            break;
+
+          // Check if-else block sequencing.
+          //
+          if (bt == line_type::cmd_else)
+          {
+            if (lt == line_type::cmd_else ||
+                lt == line_type::cmd_elif ||
+                lt == line_type::cmd_elifn)
+              fail (ll) << lt << " after " << bt;
+          }
+
+          // Parse just the condition line using pre_parse_line() in the "one"
+          // mode and into ls so that it is naturally picked up as if_cond_ on
+          // the next iteration.
+          //
+          optional<description> td;
+          bool semi (pre_parse_line (t, (tt = pt), td, &ls, true));
+          assert (ls.size () == 1 && ls.back ().type == lt);
+          assert (tt == type::newline);
+
+          // For any of these lines trailing semi or description is illegal.
+          //
+          // @@ Not the exact location of semi/colon.
+          //
+          if (semi)
+            fail (ll) << "';' after " << lt;
+
+          if (td)
+            fail (ll) << "description after " << lt;
+
+          // Make sure what comes next is another scope.
+          //
+          tt = peek (lexer_mode::first_token);
+
+          if (tt != type::lcbrace)
+            fail (ll) << "expected scope after " << lt;
+
+          // Update current if-else block.
+          //
+          switch (lt)
+          {
+          case line_type::cmd_elif:
+          case line_type::cmd_elifn: bt = line_type::cmd_elif; break;
+          case line_type::cmd_else:  bt = line_type::cmd_else; break;
+          default: break;
+          }
+        }
+
+        pre_parse_demote_group_scope (root);
+        group_->scopes.push_back (move (root));
+        return false; // We never end with a semi.
+      }
+
+      bool parser::
+      pre_parse_if_else_command (token& t, type& tt,
+                                 optional<description>& d,
+                                 lines& ls)
+      {
+        // enter: peeked first token of next line (type in tt)
+        // leave: newline
+
+        // Parse lines until we see closing 'end'. Nested if-else blocks are
+        // handled recursively.
+        //
+        for (line_type bt (line_type::cmd_if); // Current block.
+             ;
+             tt = peek (lexer_mode::first_token))
+        {
+          const location ll (get_location (peeked ()));
+
+          switch (tt)
+          {
+          case type::colon:
+            fail (ll) << "description inside " << bt << endf;
+          case type::eos:
+          case type::rcbrace:
+          case type::lcbrace:
+            fail (ll) << "expected closing 'end'" << endf;
+          case type::plus:
+            fail (ll) << "setup command inside " << bt << endf;
+          case type::minus:
+            fail (ll) << "teardown command inside " << bt << endf;
+          }
+
+          // Parse one line. Note that this one line can still be multiple
+          // lines in case of if-else. In this case we want to view it as
+          // cmd_if, not cmd_end. Thus remember the start position of the
+          // next logical line.
+          //
+          size_t i (ls.size ());
+
+          optional<description> td;
+          bool semi (pre_parse_line (t, tt, td, &ls, true));
+          assert (tt == type::newline);
+
+          line_type lt (ls[i].type);
+
+          // First take care of 'end'.
+          //
+          if (lt == line_type::cmd_end)
+          {
+            if (td)
+            {
+              if (d)
+                fail (ll) << "both leading and trailing descriptions";
+
+              d = move (td);
+            }
+
+            return semi;
+          }
+
+          // For any other line trailing semi or description is illegal.
+          //
+          // @@ Not the exact location of semi/colon.
+          //
+          if (semi)
+            fail (ll) << "';' inside " << bt;
+
+          if (td)
+            fail (ll) << "description inside " << bt;
+
+          // Check if-else block sequencing.
+          //
+          if (bt == line_type::cmd_else)
+          {
+            if (lt == line_type::cmd_else ||
+                lt == line_type::cmd_elif ||
+                lt == line_type::cmd_elifn)
+              fail (ll) << lt << " after " << bt;
+          }
+
+          // Update current if-else block.
+          //
+          switch (lt)
+          {
+          case line_type::cmd_elif:
+          case line_type::cmd_elifn: bt = line_type::cmd_elif; break;
+          case line_type::cmd_else:  bt = line_type::cmd_else; break;
+          default: break;
+          }
+        }
+      }
+
+      void parser::
+      pre_parse_directive (token& t, type& tt)
+      {
+        // enter: directive name
+        // leave: newline
+
+        string d (t.value);
+        location l (get_location (t));
+        next (t, tt);
+
+        // Suspend pre-parsing since we want to really parse the line, with
+        // expansion, etc. Also parse the whole line in one go.
+        //
+        names args;
+
+        if (tt != type::newline)
+        {
+          pre_parse_ = false;
+          args = parse_names (t, tt,
+                              pattern_mode::expand,
+                              false,
+                              "directive argument",
+                              nullptr);
+          pre_parse_ = true;
+        }
+
+        if (tt != type::newline)
+          fail (t) << t << " after directive";
+
+        if (d == "include")
+          pre_parse_include_line (move (args), move (l));
+        else
+          assert (false); // Unhandled directive.
+      }
+
+      void parser::
+      pre_parse_include_line (names args, location dl)
+      {
+        auto i (args.begin ());
+
+        // Process options.
+        //
+        bool once (false);
+        for (; i != args.end () && i->simple (); ++i)
+        {
+          if (i->value == "--once")
+            once = true;
+          else
+            break;
+        }
+
+        // Process arguments.
+        //
+        auto include = [&dl, once, this] (string n) // throw invalid_path
+        {
+          // It may be tempting to use relative paths in diagnostics but it
+          // most likely will be misguided.
+          //
+          auto enter_path = [this] (string n) -> const path&
+          {
+            path p (move (n));
+
+            if (p.relative ())
+              p = path_->directory () / p;
+
+            p.normalize ();
+
+            return *script_->paths_.insert (move (p)).first;
+          };
+
+          const path& p (enter_path (move (n)));
+
+          if (include_set_->insert (p).second || !once)
+          {
+            try
+            {
+              ifdstream ifs (p);
+              lexer l (ifs, p, lexer_mode::command_line);
+
+              const path* op (path_);
+              path_ = &p;
+
+              lexer* ol (lexer_);
+              set_lexer (&l);
+
+              string oip (id_prefix_);
+              id_prefix_ += to_string (dl.line);
+              id_prefix_ += '-';
+              id_prefix_ += p.leaf ().base ().string ();
+              id_prefix_ += '-';
+
+              token t (pre_parse_scope_body ());
+
+              if (t.type != type::eos)
+                fail (t) << "stray " << t;
+
+              id_prefix_ = oip;
+              set_lexer (ol);
+              path_ = op;
+            }
+            catch (const io_error& e)
+            {
+              fail (dl) << "unable to read testscript " << p << ": " << e;
+            }
+          }
+        };
+
+        for (; i != args.end (); ++i)
+        {
+          name& n (*i);
+
+          try
+          {
+            if (n.simple () && !n.empty ())
+            {
+              include (move (n.value));
+              continue;
+            }
+          }
+          catch (const invalid_path&) {} // Fall through.
+
+          diag_record dr (fail (dl));
+          dr << "invalid testscript include path ";
+          to_stream (dr.os, n, true); // Quote.
+        }
+      }
+
+      description parser::
+      pre_parse_leading_description (token& t, type& tt)
+      {
+        // enter: peeked at colon (type in tt)
+        // leave: peeked at in the first_token mode (type in tt)
+
+        assert (tt == type::colon);
+
+        description r;
+        location loc (get_location (peeked ()));
+
+        string sp;     // Strip prefix.
+        size_t sn (0); // Strip prefix length.
+
+        for (size_t ln (1); tt == type::colon; ++ln)
+        {
+          next (t, tt); // Get ':'.
+
+          mode (lexer_mode::description_line);
+          next (t, tt);
+
+          // If it is empty, then we get newline right away.
+          //
+          const string& l (tt == type::word ? t.value : string ());
+
+          if (tt == type::word)
+            next (t, tt); // Get newline.
+
+          assert (tt == type::newline);
+
+          // If this is the first line, then get the "strip prefix", i.e.,
+          // the beginning of the line that contains only whitespaces. If
+          // the subsequent lines start with the same prefix, then we strip
+          // it.
+          //
+          if (ln == 1)
+          {
+            sn = l.find_first_not_of (" \t");
+            sp.assign (l, 0, sn == string::npos ? (sn = 0) : sn);
+          }
+
+          // Apply strip prefix.
+          //
+          size_t i (l.compare (0, sn, sp) == 0 ? sn : 0);
+
+          // Strip trailing whitespaces, as a courtesy to the user.
+          //
+          size_t j (l.find_last_not_of (" \t"));
+          j = j != string::npos ? j + 1 : i;
+
+          size_t n (j - i); // [i, j) is our data.
+
+          if (ln == 1)
+          {
+            // First line. Ignore if it's blank.
+            //
+            if (n == 0)
+              --ln; // Stay as if on the first line.
+            else
+            {
+              // Otherwise, see if it is the id. Failed that we assume it is
+              // the summary until we see the next line.
+              //
+              (l.find_first_of (" \t.", i) >= j ? r.id : r.summary).
+                assign (l, i, n);
+
+              // If this is an id then validate it.
+              //
+              if (!r.id.empty ())
+              {
+                for (char c: r.id)
+                {
+                  if (!(alnum (c) || c == '_' || c == '-' || c == '+'))
+                    fail (loc) << "illegal character '" << c
+                               << "' in test id '" << r.id << "'";
+                }
+              }
+            }
+          }
+          else if (ln == 2)
+          {
+            // If this is a blank then whatever we have in id/summary is good.
+            // Otherwise, if we have id, then assume this is summary until we
+            // see the next line. And if not, then move what we (wrongly)
+            // assumed to be the summary to details.
+            //
+            if (n != 0)
+            {
+              if (!r.id.empty ())
+                r.summary.assign (l, i, n);
+              else
+              {
+                r.details = move (r.summary);
+                r.details += '\n';
+                r.details.append (l, i, n);
+
+                r.summary.clear ();
+              }
+            }
+          }
+          // Don't treat line 3 as special if we have given up on id/summary.
+          //
+          else if (ln == 3 && r.details.empty ())
+          {
+            // If this is a blank and we have id and/or summary, then we are
+            // good. Otherwise, if we have both, then move what we (wrongly)
+            // assumed to be id and summary to details.
+            //
+            if (n != 0)
+            {
+              if (!r.id.empty () && !r.summary.empty ())
+              {
+                r.details = move (r.id);
+                r.details += '\n';
+                r.details += r.summary;
+                r.details += '\n';
+
+                r.id.clear ();
+                r.summary.clear ();
+              }
+
+              r.details.append (l, i, n);
+            }
+          }
+          else
+          {
+            if (!r.details.empty ())
+              r.details += '\n';
+
+            r.details.append (l, i, n);
+          }
+
+          tt = peek (lexer_mode::first_token);
+        }
+
+        // Zap trailing newlines in the details.
+        //
+        size_t p (r.details.find_last_not_of ('\n'));
+        if (p != string::npos && ++p != r.details.size ())
+          r.details.resize (p);
+
+        if (r.empty ())
+          fail (loc) << "empty description";
+
+        // Insert id into the id map if we have one.
+        //
+        if (!r.id.empty ())
+          insert_id (r.id, loc);
+
+        return r;
+      }
+
+      description parser::
+      parse_trailing_description (token& t, type& tt)
+      {
+        // enter: colon
+        // leave: newline
+
+        // Parse one-line trailing description.
+        //
+        description r;
+
+        // @@ Would be nice to omit trailing description from replay.
+        //
+        const location loc (get_location (t));
+
+        mode (lexer_mode::description_line);
+        next (t, tt);
+
+        // If it is empty, then we will get newline right away.
+        //
+        if (tt == type::word)
+        {
+          string l (move (t.value));
+          trim (l); // Strip leading/trailing whitespaces.
+
+          // Decide whether this is id or summary.
+          //
+          (l.find_first_of (" \t") == string::npos ? r.id : r.summary) =
+            move (l);
+
+          next (t, tt); // Get newline.
+        }
+
+        assert (tt == type::newline); // Lexer mode invariant.
+
+        if (r.empty ())
+          fail (loc) << "empty description";
+
+        // Insert id into the id map if we have one.
+        //
+        if (pre_parse_ && !r.id.empty ())
+          insert_id (r.id, loc);
+
+        return r;
+      }
+
+      value parser::
+      parse_variable_line (token& t, type& tt)
+      {
+        // enter: assignment
+        // leave: newline or semi
+
+        // We cannot reuse the value mode since it will recognize { which we
+        // want to treat as a literal.
+        //
+        mode (lexer_mode::variable_line);
+        next (t, tt);
+
+        // Parse value attributes if any. Note that it's ok not to have
+        // anything after the attributes (e.g., foo=[null]).
+        //
+        attributes_push (t, tt, true);
+
+        // @@ PAT: Should we expand patterns? Note that it will only be
+        // simple ones since we have disabled {}. Also, what would be the
+        // pattern base directory?
+        //
+        return tt != type::newline && tt != type::semi
+          ? parse_value (t, tt,
+                         pattern_mode::ignore,
+                         "variable value",
+                         nullptr)
+          : value (names ());
+      }
+
+      command_expr parser::
+      parse_command_line (token& t, type& tt)
+      {
+        // enter: first token of the command line
+        // leave: <newline>
+
+        // Note: this one is only used during execution.
+
+        pair<command_expr, here_docs> p (parse_command_expr (t, tt));
+
+        switch (tt)
+        {
+        case type::colon: parse_trailing_description (t, tt); break;
+        case type::semi: next (t, tt); break; // Get newline.
+        }
+
+        assert (tt == type::newline);
+
+        parse_here_documents (t, tt, p);
+        assert (tt == type::newline);
+
+        return move (p.first);
+      }
+
+      // Parse the regular expression representation (non-empty string value
+      // framed with introducer characters and optionally followed by flag
+      // characters from the {di} set, for example '/foo/id') into
+      // components. Also return end-of-parsing position if requested,
+      // otherwise treat any unparsed characters left as an error.
+      //
+      struct regex_parts
+      {
+        string value;
+        char   intro;
+        string flags; // Combination of characters from {di} set.
+
+        // Create a special empty object.
+        //
+        regex_parts (): intro ('\0') {}
+
+        regex_parts (string v, char i, string f)
+            : value (move (v)), intro (i), flags (move (f)) {}
+      };
+
+      static regex_parts
+      parse_regex (const string& s,
+                   const location& l,
+                   const char* what,
+                   size_t* end = nullptr)
+      {
+        if (s.empty ())
+          fail (l) << "no introducer character in " << what;
+
+        size_t p (s.find (s[0], 1)); // Find terminating introducer.
+
+        if (p == string::npos)
+          fail (l) << "no closing introducer character in " << what;
+
+        size_t rn (p - 1); // Regex length.
+        if (rn == 0)
+          fail (l) << what << " is empty";
+
+        // Find end-of-flags position.
+        //
+        size_t fp (++p); // Save flags starting position.
+        for (char c; (c = s[p]) == 'd' || c == 'i'; ++p) ;
+
+        // If string end is not reached then report invalid flags, unless
+        // end-of-parsing position is requested (which means regex is just a
+        // prefix).
+        //
+        if (s[p] != '\0' && end == nullptr)
+          fail (l) << "junk at the end of " << what;
+
+        if (end != nullptr)
+          *end = p;
+
+        return regex_parts (string (s, 1, rn), s[0], string (s, fp, p - fp));
+      }
+
+      pair<command_expr, parser::here_docs> parser::
+      parse_command_expr (token& t, type& tt)
+      {
+        // enter: first token of the command line
+        // leave: <newline>
+
+        command_expr expr;
+
+        // OR-ed to an implied false for the first term.
+        //
+        expr.push_back ({expr_operator::log_or, command_pipe ()});
+
+        command c; // Command being assembled.
+
+        // Make sure the command makes sense.
+        //
+        auto check_command = [&c, this] (const location& l, bool last)
+        {
+          if (c.out.type == redirect_type::merge &&
+              c.err.type == redirect_type::merge)
+            fail (l) << "stdout and stderr redirected to each other";
+
+          if (!last && c.out.type != redirect_type::none)
+            fail (l) << "stdout is both redirected and piped";
+        };
+
+        // Check that the introducer character differs from '/' if the
+        // portable path modifier is specified. Must be called before
+        // parse_regex() (see below) to make sure its diagnostics is
+        // meaningful.
+        //
+        // Note that the portable path modifier assumes '/' to be a valid
+        // regex character and so makes it indistinguishable from the
+        // terminating introducer.
+        //
+        auto check_regex_mod = [this] (const string& mod,
+                                       const string& re,
+                                       const location& l,
+                                       const char* what)
+        {
+          // Handles empty regex properly.
+          //
+          if (mod.find ('/') != string::npos && re[0] == '/')
+            fail (l) << "portable path modifier and '/' introducer in "
+                     << what;
+        };
+
+        // Pending positions where the next word should go.
+        //
+        enum class pending
+        {
+          none,
+          program,
+          in_string,
+          in_document,
+          in_file,
+          out_merge,
+          out_string,
+          out_str_regex,
+          out_document,
+          out_doc_regex,
+          out_file,
+          err_merge,
+          err_string,
+          err_str_regex,
+          err_document,
+          err_doc_regex,
+          err_file,
+          clean
+        };
+        pending p (pending::program);
+        string mod;   // Modifiers for pending in_* and out_* positions.
+        here_docs hd; // Expected here-documents.
+
+        // Add the next word to either one of the pending positions or to
+        // program arguments by default.
+        //
+        auto add_word = [&c, &p, &mod, &check_regex_mod, this] (
+          string&& w, const location& l)
+        {
+          auto add_merge = [&l, this] (redirect& r, const string& w, int fd)
+          {
+            try
+            {
+              size_t n;
+              if (stoi (w, &n) == fd && n == w.size ())
+              {
+                r.fd = fd;
+                return;
+              }
+            }
+            catch (const exception&) {} // Fall through.
+
+            fail (l) << (fd == 1 ? "stderr" : "stdout") << " merge redirect "
+                     << "file descriptor must be " << fd;
+          };
+
+          auto add_here_str = [] (redirect& r, string&& w)
+          {
+            if (r.modifiers.find (':') == string::npos)
+              w += '\n';
+            r.str = move (w);
+          };
+
+          auto add_here_str_regex = [&l, &check_regex_mod] (
+            redirect& r, int fd, string&& w)
+          {
+            const char* what (nullptr);
+            switch (fd)
+            {
+            case 1: what = "stdout regex redirect"; break;
+            case 2: what = "stderr regex redirect"; break;
+            }
+
+            check_regex_mod (r.modifiers, w, l, what);
+
+            regex_parts rp (parse_regex (w, l, what));
+
+            regex_lines& re (r.regex);
+            re.intro = rp.intro;
+
+            re.lines.emplace_back (
+              l.line, l.column, move (rp.value), move (rp.flags));
+
+            // Add final blank line unless suppressed.
+            //
+            // Note that the position is synthetic, but that's ok as we don't
+            // expect any diagnostics to refer this line.
+            //
+            if (r.modifiers.find (':') == string::npos)
+              re.lines.emplace_back (l.line, l.column, string (), false);
+          };
+
+          auto parse_path = [&l, this] (string&& w, const char* what) -> path
+          {
+            try
+            {
+              path p (move (w));
+
+              if (!p.empty ())
+              {
+                p.normalize ();
+                return p;
+              }
+
+              fail (l) << "empty " << what << endf;
+            }
+            catch (const invalid_path& e)
+            {
+              fail (l) << "invalid " << what << " '" << e.path << "'" << endf;
+            }
+          };
+
+          auto add_file = [&parse_path] (redirect& r, int fd, string&& w)
+          {
+            const char* what (nullptr);
+            switch (fd)
+            {
+            case 0: what = "stdin redirect path";  break;
+            case 1: what = "stdout redirect path"; break;
+            case 2: what = "stderr redirect path"; break;
+            }
+
+            r.file.path = parse_path (move (w), what);
+          };
+
+          switch (p)
+          {
+          case pending::none: c.arguments.push_back (move (w)); break;
+          case pending::program:
+            c.program = parse_path (move (w), "program path");
+            break;
+
+          case pending::out_merge: add_merge (c.out, w, 2); break;
+          case pending::err_merge: add_merge (c.err, w, 1); break;
+
+          case pending::in_string:  add_here_str (c.in,  move (w)); break;
+          case pending::out_string: add_here_str (c.out, move (w)); break;
+          case pending::err_string: add_here_str (c.err, move (w)); break;
+
+          case pending::out_str_regex:
+            {
+              add_here_str_regex (c.out, 1, move (w));
+              break;
+            }
+          case pending::err_str_regex:
+            {
+              add_here_str_regex (c.err, 2, move (w));
+              break;
+            }
+
+            // These are handled specially below.
+            //
+          case pending::in_document:
+          case pending::out_document:
+          case pending::err_document:
+          case pending::out_doc_regex:
+          case pending::err_doc_regex: assert (false); break;
+
+          case pending::in_file:  add_file (c.in,  0, move (w)); break;
+          case pending::out_file: add_file (c.out, 1, move (w)); break;
+          case pending::err_file: add_file (c.err, 2, move (w)); break;
+
+          case pending::clean:
+            {
+              cleanup_type t;
+              switch (mod[0]) // Ok, if empty
+              {
+              case '!': t = cleanup_type::never;  break;
+              case '?': t = cleanup_type::maybe;  break;
+              default:  t = cleanup_type::always; break;
+              }
+
+              c.cleanups.push_back (
+                {t, parse_path (move (w), "cleanup path")});
+              break;
+            }
+          }
+
+          p = pending::none;
+          mod.clear ();
+        };
+
+        // Make sure we don't have any pending positions to fill.
+        //
+        auto check_pending = [&p, this] (const location& l)
+        {
+          const char* what (nullptr);
+
+          switch (p)
+          {
+          case pending::none:                                            break;
+          case pending::program:      what = "program";                  break;
+          case pending::in_string:    what = "stdin here-string";        break;
+          case pending::in_document:  what = "stdin here-document end";  break;
+          case pending::in_file:      what = "stdin file";               break;
+          case pending::out_merge:    what = "stdout file descriptor";   break;
+          case pending::out_string:   what = "stdout here-string";       break;
+          case pending::out_document: what = "stdout here-document end"; break;
+          case pending::out_file:     what = "stdout file";              break;
+          case pending::err_merge:    what = "stderr file descriptor";   break;
+          case pending::err_string:   what = "stderr here-string";       break;
+          case pending::err_document: what = "stderr here-document end"; break;
+          case pending::err_file:     what = "stderr file";              break;
+          case pending::clean:        what = "cleanup path";             break;
+
+          case pending::out_str_regex:
+            {
+              what = "stdout here-string regex";
+              break;
+            }
+          case pending::err_str_regex:
+            {
+              what = "stderr here-string regex";
+              break;
+            }
+          case pending::out_doc_regex:
+            {
+              what = "stdout here-document regex end";
+              break;
+            }
+          case pending::err_doc_regex:
+            {
+              what = "stderr here-document regex end";
+              break;
+            }
+          }
+
+          if (what != nullptr)
+            fail (l) << "missing " << what;
+        };
+
+        // Parse the redirect operator.
+        //
+        auto parse_redirect =
+          [&c, &expr, &p, &mod, this] (token& t, const location& l)
+        {
+          // Our semantics is the last redirect seen takes effect.
+          //
+          assert (p == pending::none && mod.empty ());
+
+          // See if we have the file descriptor.
+          //
+          unsigned long fd (3);
+          if (!t.separated)
+          {
+            if (c.arguments.empty ())
+              fail (l) << "missing redirect file descriptor";
+
+            const string& s (c.arguments.back ());
+
+            try
+            {
+              size_t n;
+              fd = stoul (s, &n);
+
+              if (n != s.size () || fd > 2)
+                throw invalid_argument (string ());
+            }
+            catch (const exception&)
+            {
+              fail (l) << "invalid redirect file descriptor '" << s << "'";
+            }
+
+            c.arguments.pop_back ();
+          }
+
+          type tt (t.type);
+
+          // Validate/set default file descriptor.
+          //
+          switch (tt)
+          {
+          case type::in_pass:
+          case type::in_null:
+          case type::in_str:
+          case type::in_doc:
+          case type::in_file:
+            {
+              if ((fd = fd == 3 ? 0 : fd) != 0)
+                fail (l) << "invalid in redirect file descriptor " << fd;
+
+              if (!expr.back ().pipe.empty ())
+                fail (l) << "stdin is both piped and redirected";
+
+              break;
+            }
+          case type::out_pass:
+          case type::out_null:
+          case type::out_trace:
+          case type::out_merge:
+          case type::out_str:
+          case type::out_doc:
+          case type::out_file_cmp:
+          case type::out_file_ovr:
+          case type::out_file_app:
+            {
+              if ((fd = fd == 3 ? 1 : fd) == 0)
+                fail (l) << "invalid out redirect file descriptor " << fd;
+
+              break;
+            }
+          }
+
+          mod = move (t.value);
+
+          redirect_type rt (redirect_type::none);
+          switch (tt)
+          {
+          case type::in_pass:
+          case type::out_pass:  rt = redirect_type::pass;  break;
+
+          case type::in_null:
+          case type::out_null:  rt = redirect_type::null;  break;
+
+          case type::out_trace: rt = redirect_type::trace; break;
+
+          case type::out_merge: rt = redirect_type::merge; break;
+
+          case type::in_str:
+          case type::out_str:
+            {
+              bool re (mod.find ('~') != string::npos);
+              assert (tt == type::out_str || !re);
+
+              rt = re
+                ? redirect_type::here_str_regex
+                : redirect_type::here_str_literal;
+
+              break;
+            }
+
+          case type::in_doc:
+          case type::out_doc:
+            {
+              bool re (mod.find ('~') != string::npos);
+              assert (tt == type::out_doc || !re);
+
+              rt = re
+                ? redirect_type::here_doc_regex
+                : redirect_type::here_doc_literal;
+
+              break;
+            }
+
+          case type::in_file:
+          case type::out_file_cmp:
+          case type::out_file_ovr:
+          case type::out_file_app: rt = redirect_type::file; break;
+          }
+
+          redirect& r (fd == 0 ? c.in : fd == 1 ? c.out : c.err);
+          r = redirect (rt);
+
+          // Don't move as still may be used for pending here-document end
+          // marker processing.
+          //
+          r.modifiers = mod;
+
+          switch (rt)
+          {
+          case redirect_type::none:
+          case redirect_type::pass:
+          case redirect_type::null:
+          case redirect_type::trace:
+            break;
+          case redirect_type::merge:
+            switch (fd)
+            {
+            case 0: assert (false);         break;
+            case 1: p = pending::out_merge; break;
+            case 2: p = pending::err_merge; break;
+            }
+            break;
+          case redirect_type::here_str_literal:
+            switch (fd)
+            {
+            case 0: p = pending::in_string;  break;
+            case 1: p = pending::out_string; break;
+            case 2: p = pending::err_string; break;
+            }
+            break;
+          case redirect_type::here_str_regex:
+            switch (fd)
+            {
+            case 0: assert (false);             break;
+            case 1: p = pending::out_str_regex; break;
+            case 2: p = pending::err_str_regex; break;
+            }
+            break;
+          case redirect_type::here_doc_literal:
+            switch (fd)
+            {
+            case 0: p = pending::in_document;  break;
+            case 1: p = pending::out_document; break;
+            case 2: p = pending::err_document; break;
+            }
+            break;
+          case redirect_type::here_doc_regex:
+            switch (fd)
+            {
+            case 0: assert (false);             break;
+            case 1: p = pending::out_doc_regex; break;
+            case 2: p = pending::err_doc_regex; break;
+            }
+            break;
+          case redirect_type::file:
+            switch (fd)
+            {
+            case 0: p = pending::in_file;  break;
+            case 1: p = pending::out_file; break;
+            case 2: p = pending::err_file; break;
+            }
+
+            // Also sets for stdin, but this is harmless.
+            //
+            r.file.mode = tt == type::out_file_ovr
+              ? redirect_fmode::overwrite
+              : (tt == type::out_file_app
+                 ? redirect_fmode::append
+                 : redirect_fmode::compare);
+
+            break;
+
+          case redirect_type::here_doc_ref: assert (false); break;
+          }
+        };
+
+        // Set pending cleanup type.
+        //
+        auto parse_clean = [&p, &mod] (token& t)
+        {
+          p = pending::clean;
+          mod = move (t.value);
+        };
+
+        const location ll (get_location (t)); // Line location.
+
+        // Keep parsing chunks of the command line until we see one of the
+        // "terminators" (newline, semicolon, exit status comparison, etc).
+        //
+        location l (ll);
+        names ns; // Reuse to reduce allocations.
+
+        for (bool done (false); !done; l = get_location (t))
+        {
+          switch (tt)
+          {
+          case type::semi:
+          case type::colon:
+          case type::newline:
+            {
+              done = true;
+              break;
+            }
+
+          case type::equal:
+          case type::not_equal:
+            {
+              if (!pre_parse_)
+                check_pending (l);
+
+              c.exit = parse_command_exit (t, tt);
+
+              // Only a limited set of things can appear after the exit status
+              // so we check this here.
+              //
+              switch (tt)
+              {
+              case type::semi:
+              case type::colon:
+              case type::newline:
+
+              case type::pipe:
+              case type::log_or:
+              case type::log_and:
+                break;
+              default:
+                fail (t) << "unexpected " << t << " after command exit status";
+              }
+
+              break;
+            }
+
+          case type::pipe:
+          case type::log_or:
+          case type::log_and:
+
+          case type::in_pass:
+          case type::out_pass:
+
+          case type::in_null:
+          case type::out_null:
+
+          case type::out_trace:
+
+          case type::out_merge:
+
+          case type::in_str:
+          case type::in_doc:
+          case type::out_str:
+          case type::out_doc:
+
+          case type::in_file:
+          case type::out_file_cmp:
+          case type::out_file_ovr:
+          case type::out_file_app:
+
+          case type::clean:
+            {
+              if (pre_parse_)
+              {
+                // The only things we need to handle here are the here-document
+                // and here-document regex end markers since we need to know
+                // how many of them to pre-parse after the command.
+                //
+                switch (tt)
+                {
+                case type::in_doc:
+                case type::out_doc:
+                  mod = move (t.value);
+
+                  bool re (mod.find ('~') != string::npos);
+                  const char* what (re
+                                    ? "here-document regex end marker"
+                                    : "here-document end marker");
+
+                  // We require the end marker to be a literal, unquoted word.
+                  // In particularm, we don't allow quoted because of cases
+                  // like foo"$bar" (where we will see word 'foo').
+                  //
+                  next (t, tt);
+
+                  // We require the end marker to be an unquoted or completely
+                  // quoted word. The complete quoting becomes important for
+                  // cases like foo"$bar" (where we will see word 'foo').
+                  //
+                  // For good measure we could have also required it to be
+                  // separated from the following token, but out grammar
+                  // allows one to write >>EOO;. The problematic sequence
+                  // would be >>FOO$bar -- on reparse it will be expanded
+                  // as a single word.
+                  //
+                  if (tt != type::word || t.value.empty ())
+                    fail (t) << "expected " << what;
+
+                  peek ();
+                  const token& p (peeked ());
+                  if (!p.separated)
+                  {
+                    switch (p.type)
+                    {
+                    case type::dollar:
+                    case type::lparen:
+                      fail (p) << what << " must be literal";
+                    }
+                  }
+
+                  quote_type qt (t.qtype);
+                  switch (qt)
+                  {
+                  case quote_type::unquoted:
+                    qt = quote_type::single; // Treat as single-quoted.
+                    break;
+                  case quote_type::single:
+                  case quote_type::double_:
+                    if (t.qcomp)
+                      break;
+                    // Fall through.
+                  case quote_type::mixed:
+                    fail (t) << "partially-quoted " << what;
+                  }
+
+                  regex_parts r;
+                  string end (move (t.value));
+
+                  if (re)
+                  {
+                    check_regex_mod (mod, end, l, what);
+
+                    r = parse_regex (end, l, what);
+                    end = move (r.value); // The "cleared" end marker.
+                  }
+
+                  bool literal (qt == quote_type::single);
+                  bool shared (false);
+
+                  for (const auto& d: hd)
+                  {
+                    if (d.end == end)
+                    {
+                      auto check = [&t, &end, &re, this] (bool c,
+                                                          const char* what)
+                      {
+                        if (!c)
+                          fail (t) << "different " << what
+                                   << " for shared here-document "
+                                   << (re ? "regex '" : "'") << end << "'";
+                      };
+
+                      check (d.modifiers == mod, "modifiers");
+                      check (d.literal == literal, "quoting");
+
+                      if (re)
+                      {
+                        check (d.regex == r.intro, "introducers");
+                        check (d.regex_flags == r.flags, "global flags");
+                      }
+
+                      shared = true;
+                      break;
+                    }
+                  }
+
+                  if (!shared)
+                    hd.push_back (
+                      here_doc {
+                        {},
+                        move (end),
+                        literal,
+                        move (mod),
+                        r.intro, move (r.flags)});
+
+                  break;
+                }
+
+                next (t, tt);
+                break;
+              }
+
+              // If this is one of the operators/separators, check that we
+              // don't have any pending locations to be filled.
+              //
+              check_pending (l);
+
+              // Note: there is another one in the inner loop below.
+              //
+              switch (tt)
+              {
+              case type::pipe:
+              case type::log_or:
+              case type::log_and:
+                {
+                  // Check that the previous command makes sense.
+                  //
+                  check_command (l, tt != type::pipe);
+                  expr.back ().pipe.push_back (move (c));
+
+                  c = command ();
+                  p = pending::program;
+
+                  if (tt != type::pipe)
+                  {
+                    expr_operator o (tt == type::log_or
+                                     ? expr_operator::log_or
+                                     : expr_operator::log_and);
+                    expr.push_back ({o, command_pipe ()});
+                  }
+
+                  break;
+                }
+
+              case type::in_pass:
+              case type::out_pass:
+
+              case type::in_null:
+              case type::out_null:
+
+              case type::out_trace:
+
+              case type::out_merge:
+
+              case type::in_str:
+              case type::in_doc:
+              case type::out_str:
+              case type::out_doc:
+
+              case type::in_file:
+              case type::out_file_cmp:
+              case type::out_file_ovr:
+              case type::out_file_app:
+                {
+                  parse_redirect (t, l);
+                  break;
+                }
+
+              case type::clean:
+                {
+                  parse_clean (t);
+                  break;
+                }
+
+              default: assert (false); break;
+              }
+
+              next (t, tt);
+              break;
+            }
+          default:
+            {
+              // Here-document end markers are literal (we verified that above
+              // during pre-parsing) and we need to know whether they were
+              // quoted. So handle this case specially.
+              //
+              {
+                int fd;
+                switch (p)
+                {
+                case pending::in_document:   fd =  0; break;
+                case pending::out_document:
+                case pending::out_doc_regex: fd =  1; break;
+                case pending::err_document:
+                case pending::err_doc_regex: fd =  2; break;
+                default:                     fd = -1; break;
+                }
+
+                if (fd != -1)
+                {
+                  here_redirect rd {
+                    expr.size () - 1, expr.back ().pipe.size (), fd};
+
+                  string end (move (t.value));
+
+                  regex_parts r;
+
+                  if (p == pending::out_doc_regex ||
+                      p == pending::err_doc_regex)
+                  {
+                    // We can't fail here as we already parsed all the end
+                    // markers during pre-parsing stage, and so no need in the
+                    // description.
+                    //
+                    r = parse_regex (end, l, "");
+                    end = move (r.value); // The "cleared" end marker.
+                  }
+
+                  bool shared (false);
+                  for (auto& d: hd)
+                  {
+                    // No need to check that redirects that share here-document
+                    // have the same modifiers, etc. That have been done during
+                    // pre-parsing.
+                    //
+                    if (d.end == end)
+                    {
+                      d.redirects.emplace_back (rd);
+                      shared = true;
+                      break;
+                    }
+                  }
+
+                  if (!shared)
+                    hd.push_back (
+                      here_doc {
+                        {rd},
+                        move (end),
+                        (t.qtype == quote_type::unquoted ||
+                         t.qtype == quote_type::single),
+                        move (mod),
+                        r.intro, move (r.flags)});
+
+                  p = pending::none;
+                  mod.clear ();
+
+                  next (t, tt);
+                  break;
+                }
+              }
+
+              // Parse the next chunk as simple names to get expansion, etc.
+              // Note that we do it in the chunking mode to detect whether
+              // anything in each chunk is quoted.
+              //
+              // @@ PAT: should we support pattern expansion? This is even
+              // fuzzier than the variable case above. Though this is the
+              // shell semantics. Think what happens when we do rm *.txt?
+              //
+              reset_quoted (t);
+              parse_names (t, tt,
+                           ns,
+                           pattern_mode::ignore,
+                           true,
+                           "command line",
+                           nullptr);
+
+              if (pre_parse_) // Nothing else to do if we are pre-parsing.
+                break;
+
+              // Process what we got. Determine whether anything inside was
+              // quoted (note that the current token is "next" and is not part
+              // of this).
+              //
+              bool q ((quoted () -
+                       (t.qtype != quote_type::unquoted ? 1 : 0)) != 0);
+
+              for (name& n: ns)
+              {
+                string s;
+
+                try
+                {
+                  s = value_traits<string>::convert (move (n), nullptr);
+                }
+                catch (const invalid_argument&)
+                {
+                  diag_record dr (fail (l));
+                  dr << "invalid string value ";
+                  to_stream (dr.os, n, true); // Quote.
+                }
+
+                // If it is a quoted chunk, then we add the word as is.
+                // Otherwise we re-lex it. But if the word doesn't contain any
+                // interesting characters (operators plus quotes/escapes),
+                // then no need to re-lex.
+                //
+                // NOTE: update quoting (script.cxx:to_stream_q()) if adding
+                // any new characters.
+                //
+                if (q || s.find_first_of ("|&<>\'\"\\") == string::npos)
+                  add_word (move (s), l);
+                else
+                {
+                  // If the chunk re-parsing results in error, our diagnostics
+                  // will look like this:
+                  //
+                  // <string>:1:4: error: stdout merge redirect file descriptor must be 2
+                  //   testscript:2:5: info: while parsing string '1>&a'
+                  //
+                  auto df = make_diag_frame (
+                    [s, &l](const diag_record& dr)
+                    {
+                      dr << info (l) << "while parsing string '" << s << "'";
+                    });
+
+                  // When re-lexing we do "effective escaping" and only for
+                  // ['"\] (quotes plus the backslash itself). In particular,
+                  // there is no way to escape redirects, operators, etc. The
+                  // idea is to prefer quoting except for passing literal
+                  // quotes, for example:
+                  //
+                  // args = \"&foo\"
+                  // cmd $args               # cmd &foo
+                  //
+                  // args = 'x=\"foo bar\"'
+                  // cmd $args               # cmd x="foo bar"
+                  //
+
+                  path name ("<string>");
+                  istringstream is (s);
+                  lexer lex (is, name,
+                             lexer_mode::command_expansion,
+                             "\'\"\\");
+
+                  // Treat the first "sub-token" as always separated from what
+                  // we saw earlier.
+                  //
+                  // Note that this is not "our" token so we cannot do
+                  // fail(t). Rather we should do fail(l).
+                  //
+                  token t (lex.next ());
+                  location l (build2::get_location (t, name));
+                  t.separated = true;
+
+                  string w;
+                  bool f (t.type == type::eos); // If the whole thing is empty.
+
+                  for (; t.type != type::eos; t = lex.next ())
+                  {
+                    type tt (t.type);
+                    l = build2::get_location (t, name);
+
+                    // Re-lexing double-quotes will recognize $, ( inside as
+                    // tokens so we have to reverse them back. Since we don't
+                    // treat spaces as separators we can be sure we will get
+                    // it right.
+                    //
+                    switch (tt)
+                    {
+                    case type::dollar: w += '$'; continue;
+                    case type::lparen: w += '('; continue;
+                    }
+
+                    // Retire the current word. We need to distinguish between
+                    // empty and non-existent (e.g., > vs >"").
+                    //
+                    if (!w.empty () || f)
+                    {
+                      add_word (move (w), l);
+                      f = false;
+                    }
+
+                    if (tt == type::word)
+                    {
+                      w = move (t.value);
+                      f = true;
+                      continue;
+                    }
+
+                    // If this is one of the operators/separators, check that
+                    // we don't have any pending locations to be filled.
+                    //
+                    check_pending (l);
+
+                    // Note: there is another one in the outer loop above.
+                    //
+                    switch (tt)
+                    {
+                    case type::pipe:
+                    case type::log_or:
+                    case type::log_and:
+                      {
+                        // Check that the previous command makes sense.
+                        //
+                        check_command (l, tt != type::pipe);
+                        expr.back ().pipe.push_back (move (c));
+
+                        c = command ();
+                        p = pending::program;
+
+                        if (tt != type::pipe)
+                        {
+                          expr_operator o (tt == type::log_or
+                                           ? expr_operator::log_or
+                                           : expr_operator::log_and);
+                          expr.push_back ({o, command_pipe ()});
+                        }
+
+                        break;
+                      }
+
+                    case type::in_pass:
+                    case type::out_pass:
+
+                    case type::in_null:
+                    case type::out_null:
+
+                    case type::out_trace:
+
+                    case type::out_merge:
+
+                    case type::in_str:
+                    case type::out_str:
+
+                    case type::in_file:
+                    case type::out_file_cmp:
+                    case type::out_file_ovr:
+                    case type::out_file_app:
+                      {
+                        parse_redirect (t, l);
+                        break;
+                      }
+
+                    case type::clean:
+                      {
+                        parse_clean (t);
+                        break;
+                      }
+
+                    case type::in_doc:
+                    case type::out_doc:
+                      {
+                        fail (l) << "here-document redirect in expansion";
+                        break;
+                      }
+                    }
+                  }
+
+                  // Don't forget the last word.
+                  //
+                  if (!w.empty () || f)
+                    add_word (move (w), l);
+                }
+              }
+
+              ns.clear ();
+              break;
+            }
+          }
+        }
+
+        if (!pre_parse_)
+        {
+          // Verify we don't have anything pending to be filled and the
+          // command makes sense.
+          //
+          check_pending (l);
+          check_command (l, true);
+
+          expr.back ().pipe.push_back (move (c));
+        }
+
+        return make_pair (move (expr), move (hd));
+      }
+
+      command_exit parser::
+      parse_command_exit (token& t, type& tt)
+      {
+        // enter: equal/not_equal
+        // leave: token after exit status (one parse_names() chunk)
+
+        exit_comparison comp (tt == type::equal
+                              ? exit_comparison::eq
+                              : exit_comparison::ne);
+
+        // The next chunk should be the exit status.
+        //
+        next (t, tt);
+        location l (get_location (t));
+        names ns (parse_names (t, tt,
+                               pattern_mode::ignore,
+                               true,
+                               "exit status",
+                               nullptr));
+        unsigned long es (256);
+
+        if (!pre_parse_)
+        {
+          try
+          {
+            if (ns.size () == 1 && ns[0].simple () && !ns[0].empty ())
+              es = stoul (ns[0].value);
+          }
+          catch (const exception&) {} // Fall through.
+
+          if (es > 255)
+          {
+            diag_record dr;
+
+            dr << fail (l) << "expected exit status instead of ";
+            to_stream (dr.os, ns, true); // Quote.
+
+            dr << info << "exit status is an unsigned integer less than 256";
+          }
+        }
+
+        return command_exit {comp, static_cast<uint8_t> (es)};
+      }
+
+      void parser::
+      parse_here_documents (token& t, type& tt,
+                            pair<command_expr, here_docs>& p)
+      {
+        // enter: newline
+        // leave: newline
+
+        // Parse here-document fragments in the order they were mentioned on
+        // the command line.
+        //
+        for (here_doc& h: p.second)
+        {
+          // Switch to the here-line mode which is like single/double-quoted
+          // string but recognized the newline as a separator.
+          //
+          mode (h.literal
+                ? lexer_mode::here_line_single
+                : lexer_mode::here_line_double);
+          next (t, tt);
+
+          parsed_doc v (
+            parse_here_document (t, tt, h.end, h.modifiers, h.regex));
+
+          if (!pre_parse_)
+          {
+            assert (!h.redirects.empty ());
+            auto i (h.redirects.cbegin ());
+
+            command& c (p.first[i->expr].pipe[i->pipe]);
+            redirect& r (i->fd == 0 ? c.in : i->fd == 1 ? c.out : c.err);
+
+            if (v.re)
+            {
+              r.regex = move (v.regex);
+              r.regex.flags = move (h.regex_flags);
+            }
+            else
+              r.str = move (v.str);
+
+            r.end        = move (h.end);
+            r.end_line   = v.end_line;
+            r.end_column = v.end_column;
+
+            // Note that our references cannot be invalidated because the
+            // command_expr/command-pipe vectors already contain all their
+            // elements.
+            //
+            for (++i; i != h.redirects.cend (); ++i)
+            {
+              command& c (p.first[i->expr].pipe[i->pipe]);
+
+              (i->fd == 0 ? c.in : i->fd == 1 ? c.out : c.err) =
+                redirect (redirect_type::here_doc_ref, r);
+            }
+          }
+
+          expire_mode ();
+        }
+      }
+
+      parser::parsed_doc parser::
+      parse_here_document (token& t, type& tt,
+                           const string& em,
+                           const string& mod,
+                           char re)
+      {
+        // enter: first token on first line
+        // leave: newline (after end marker)
+
+        // String literal. Note that when decide if to terminate the previously
+        // added line with a newline, we need to distinguish a yet empty result
+        // and the one that has a single blank line added.
+        //
+        optional<string> rs;
+
+        regex_lines rre;
+
+        // Here-documents can be indented. The leading whitespaces of the end
+        // marker line (called strip prefix) determine the indentation. Every
+        // other line in the here-document should start with this prefix which
+        // is automatically stripped. The only exception is a blank line.
+        //
+        // The fact that the strip prefix is only known at the end, after
+        // seeing all the lines, is rather inconvenient. As a result, the way
+        // we implement this is a bit hackish (though there is also something
+        // elegant about it): at the end of the pre-parse stage we are going
+        // re-examine the sequence of tokens that comprise this here-document
+        // and "fix up" the first token of each line by stripping the prefix.
+        //
+        string sp;
+
+        // Remember the position of the first token in this here-document.
+        //
+        size_t ri (pre_parse_ ? replay_data_.size () - 1 : 0);
+
+        // We will use the location of the first token on the line for the
+        // regex diagnostics. At the end of the loop it will point to the
+        // beginning of the end marker.
+        //
+        location l;
+
+        while (tt != type::eos)
+        {
+          l = get_location (t);
+
+          // Check if this is the end marker. For starters, it should be a
+          // single, unquoted word followed by a newline.
+          //
+          if (tt == type::word &&
+              t.qtype == quote_type::unquoted &&
+              peek () == type::newline)
+          {
+            const string& v (t.value);
+
+            size_t vn (v.size ());
+            size_t en (em.size ());
+
+            // Then check that it ends with the end marker.
+            //
+            if (vn >= en && v.compare (vn - en, en, em) == 0)
+            {
+              // Now check that the prefix only contains whitespaces.
+              //
+              size_t n (vn - en);
+
+              if (v.find_first_not_of (" \t") >= n)
+              {
+                assert (pre_parse_ || n == 0); // Should have been stripped.
+
+                if (n != 0)
+                  sp.assign (v, 0, n); // Save the strip prefix.
+
+                next (t, tt); // Get the newline.
+                break;
+              }
+            }
+          }
+
+          // Expand the line (can be blank).
+          //
+          // @@ PAT: one could argue that if we do it in variables, then we
+          // should do it here as well. Though feels bizarre.
+          //
+          names ns (tt != type::newline
+                    ? parse_names (t, tt,
+                                   pattern_mode::ignore,
+                                   false,
+                                   "here-document line",
+                                   nullptr)
+                    : names ());
+
+          if (!pre_parse_)
+          {
+            // What shall we do if the expansion results in multiple names?
+            // For, example if the line contains just the variable expansion
+            // and it is of type strings. Adding all the elements space-
+            // separated seems like the natural thing to do.
+            //
+            string s;
+            for (auto b (ns.begin ()), i (b); i != ns.end (); ++i)
+            {
+              string n;
+
+              try
+              {
+                n = value_traits<string>::convert (move (*i), nullptr);
+              }
+              catch (const invalid_argument&)
+              {
+                fail (l) << "invalid string value '" << *i << "'";
+              }
+
+              if (i == b)
+                s = move (n);
+              else
+              {
+                s += ' ';
+                s += n;
+              }
+            }
+
+            if (!re)
+            {
+              // Add newline after previous line.
+              //
+              if (rs)
+              {
+                *rs += '\n';
+                *rs += s;
+              }
+              else
+                rs = move (s);
+            }
+            else
+            {
+              // Due to expansion we can end up with multiple lines. If empty
+              // then will add a blank textual literal.
+              //
+              for (size_t p (0); p != string::npos; )
+              {
+                string ln;
+                size_t np (s.find ('\n', p));
+
+                if (np != string::npos)
+                {
+                  ln = string (s, p, np - p);
+                  p = np + 1;
+                }
+                else
+                {
+                  ln = string (s, p);
+                  p = np;
+                }
+
+                if (ln[0] != re) // Line doesn't start with regex introducer.
+                {
+                  // This is a line-char literal (covers blank lines as well).
+                  //
+                  // Append textual literal.
+                  //
+                  rre.lines.emplace_back (l.line, l.column, move (ln), false);
+                }
+                else // Line starts with the regex introducer.
+                {
+                  // This is a char-regex, or a sequence of line-regex syntax
+                  // characters or both (in this specific order). So we will
+                  // add regex (with optional special characters) or special
+                  // literal.
+                  //
+                  size_t p (ln.find (re, 1));
+                  if (p == string::npos)
+                  {
+                    // No regex, just a sequence of syntax characters.
+                    //
+                    string spec (ln, 1);
+                    if (spec.empty ())
+                      fail (l) << "no syntax line characters";
+
+                    // Append special literal.
+                    //
+                    rre.lines.emplace_back (
+                      l.line, l.column, move (spec), true);
+                  }
+                  else
+                  {
+                    // Regex (probably with syntax characters).
+                    //
+                    regex_parts re;
+
+                    // Empty regex is a special case repesenting a blank line.
+                    //
+                    if (p == 1)
+                      // Position to optional specal characters of an empty
+                      // regex.
+                      //
+                      ++p;
+                    else
+                      // Can't fail as all the pre-conditions verified
+                      // (non-empty with both introducers in place), so no
+                      // description required.
+                      //
+                      re = parse_regex (ln, l, "", &p);
+
+                    // Append regex with optional special characters.
+                    //
+                    rre.lines.emplace_back (l.line, l.column,
+                                            move (re.value), move (re.flags),
+                                            string (ln, p));
+                  }
+                }
+              }
+            }
+          }
+
+          // We should expand the whole line at once so this would normally be
+          // a newline but can also be an end-of-stream.
+          //
+          if (tt == type::newline)
+            next (t, tt);
+          else
+            assert (tt == type::eos);
+        }
+
+        if (tt == type::eos)
+          fail (t) << "missing here-document end marker '" << em << "'";
+
+        if (pre_parse_)
+        {
+          // Strip the indentation prefix if there is one.
+          //
+          assert (replay_ == replay::save);
+
+          if (!sp.empty ())
+          {
+            size_t sn (sp.size ());
+
+            for (; ri != replay_data_.size (); ++ri)
+            {
+              token& rt (replay_data_[ri].token);
+
+              if (rt.type == type::newline) // Blank
+                continue;
+
+              if (rt.type != type::word || rt.value.compare (0, sn, sp) != 0)
+                fail (rt) << "unindented here-document line";
+
+              // If the word is equal to the strip prefix then we have to drop
+              // the token. Note that simply making it an empty word won't
+              // have the same semantics. For instance, it would trigger
+              // concatenated expansion.
+              //
+              if (rt.value.size () == sn)
+                replay_data_.erase (replay_data_.begin () + ri);
+              else
+              {
+                rt.value.erase (0, sn);
+                rt.column += sn;
+                ++ri;
+              }
+
+              // Skip until next newline.
+              //
+              for (; replay_data_[ri].token.type != type::newline; ++ri) ;
+            }
+          }
+        }
+        else
+        {
+          // Add final newline unless suppressed.
+          //
+          if (mod.find (':') == string::npos)
+          {
+            if (re)
+              // Note that the position is synthetic, but that's ok as we don't
+              // expect any diagnostics to refer this line.
+              //
+              rre.lines.emplace_back (l.line, l.column, string (), false);
+            else if (rs)
+              *rs += '\n';
+            else
+              rs = "\n";
+          }
+
+          // Finalize regex lines.
+          //
+          if (re)
+          {
+            // Empty regex matches nothing, so not of much use.
+            //
+            if (rre.lines.empty ())
+              fail (l) << "empty here-document regex";
+
+            rre.intro  = re;
+          }
+        }
+
+        return re
+          ? parsed_doc (move (rre), l.line, l.column)
+          : parsed_doc (rs ? move (*rs) : string (), l.line, l.column);
+      }
+
+      //
+      // Execute.
+      //
+
+      void parser::
+      execute (script& s, runner& r)
+      {
+        assert (s.state == scope_state::unknown);
+
+        auto g (
+          make_exception_guard (
+            [&s] () {s.state = scope_state::failed;}));
+
+        if (!s.empty ())
+          execute (s, s, r);
+        else
+          s.state = scope_state::passed;
+      }
+
+      void parser::
+      execute (scope& sc, script& s, runner& r)
+      {
+        path_ = nullptr; // Set by replays.
+
+        pre_parse_ = false;
+
+        set_lexer (nullptr);
+
+        script_ = &s;
+        runner_ = &r;
+        group_ = nullptr;
+        id_map_ = nullptr;
+        include_set_ = nullptr;
+        scope_ = &sc;
+
+        //@@ PAT TODO: set pbase_?
+
+        exec_scope_body ();
+      }
+
+      static void
+      execute_impl (scope& s, script& scr, runner& r)
+      {
+        try
+        {
+          parser p;
+          p.execute (s, scr, r);
+        }
+        catch (const failed&)
+        {
+          s.state = scope_state::failed;
+        }
+      }
+
+      void parser::
+      exec_scope_body ()
+      {
+        size_t li (0);
+
+        runner_->enter (*scope_, scope_->start_loc_);
+
+        if (test* t = dynamic_cast<test*> (scope_))
+        {
+          exec_lines (
+            t->tests_.begin (), t->tests_.end (), li, command_type::test);
+        }
+        else if (group* g = dynamic_cast<group*> (scope_))
+        {
+          bool exec_scope (
+            exec_lines (
+              g->setup_.begin (), g->setup_.end (), li, command_type::setup));
+
+          if (exec_scope)
+          {
+            atomic_count task_count (0);
+            wait_guard wg (task_count);
+
+            // Start asynchronous execution of inner scopes keeping track of
+            // how many we have handled.
+            //
+            for (unique_ptr<scope>& chain: g->scopes)
+            {
+              // Check if this scope is ignored (e.g., via config.test).
+              //
+              if (!runner_->test (*chain) || !exec_scope)
+              {
+                chain = nullptr;
+                continue;
+              }
+
+              // Pick a scope from the if-else chain.
+              //
+              // In fact, we are going to drop all but the selected (if any)
+              // scope. This way we can re-examine the scope states later. It
+              // will also free some memory.
+              //
+              unique_ptr<scope>* ps;
+              for (ps = &chain; *ps != nullptr; ps = &ps->get ()->if_chain)
+              {
+                scope& s (**ps);
+
+                if (!s.if_cond_) // Unconditional.
+                {
+                  assert (s.if_chain == nullptr);
+                  break;
+                }
+
+                line l (move (*s.if_cond_));
+                line_type lt (l.type);
+
+                replay_data (move (l.tokens));
+
+                token t;
+                type tt;
+
+                next (t, tt);
+                const location ll (get_location (t));
+                next (t, tt); // Skip to start of command.
+
+                bool take;
+                if (lt != line_type::cmd_else)
+                {
+                  // Note: the line index count continues from setup.
+                  //
+                  command_expr ce (parse_command_line (t, tt));
+
+                  try
+                  {
+                    take = runner_->run_if (*scope_, ce, ++li, ll);
+                  }
+                  catch (const exit_scope& e)
+                  {
+                    // Bail out if the scope is exited with the failure status.
+                    // Otherwise leave the scope normally.
+                    //
+                    if (!e.status)
+                      throw failed ();
+
+                    // Stop iterating through if conditions, and stop executing
+                    // inner scopes.
+                    //
+                    exec_scope = false;
+                    replay_stop ();
+                    break;
+                  }
+
+                  if (lt == line_type::cmd_ifn || lt == line_type::cmd_elifn)
+                    take = !take;
+                }
+                else
+                {
+                  assert (tt == type::newline);
+                  take = true;
+                }
+
+                replay_stop ();
+
+                if (take)
+                {
+                  // Count the remaining conditions for the line index.
+                  //
+                  for (scope* r (s.if_chain.get ());
+                       r != nullptr &&
+                         r->if_cond_->type != line_type::cmd_else;
+                       r = r->if_chain.get ())
+                    ++li;
+
+                  s.if_chain.reset (); // Drop remaining scopes.
+                  break;
+                }
+              }
+
+              chain.reset (*ps == nullptr || (*ps)->empty () || !exec_scope
+                           ? nullptr
+                           : ps->release ());
+
+              if (chain != nullptr)
+              {
+                // Hand it off to a sub-parser potentially in another thread.
+                // But we could also have handled it serially in this parser:
+                //
+                // scope* os (scope_);
+                // scope_ = chain.get ();
+                // exec_scope_body ();
+                // scope_ = os;
+
+                // Pass our diagnostics stack (this is safe since we are going
+                // to wait for completion before unwinding the diag stack).
+                //
+                // If the scope was executed synchronously, check the status
+                // and bail out if we weren't asked to keep going.
+                //
+                // UBSan workaround.
+                //
+                const diag_frame* df (diag_frame::stack ());
+                if (!sched.async (task_count,
+                                  [] (const diag_frame* ds,
+                                      scope& s,
+                                      script& scr,
+                                      runner& r)
+                                  {
+                                    diag_frame::stack_guard dsg (ds);
+                                    execute_impl (s, scr, r);
+                                  },
+                                  df,
+                                  ref (*chain),
+                                  ref (*script_),
+                                  ref (*runner_)))
+                {
+                  // Bail out if the scope has failed and we weren't instructed
+                  // to keep going.
+                  //
+                  if (chain->state == scope_state::failed && !keep_going)
+                    throw failed ();
+                }
+              }
+            }
+
+            wg.wait ();
+
+            // Re-examine the scopes we have executed collecting their state.
+            //
+            for (const unique_ptr<scope>& chain: g->scopes)
+            {
+              if (chain == nullptr)
+                continue;
+
+              switch (chain->state)
+              {
+              case scope_state::passed: break;
+              case scope_state::failed: throw failed ();
+              default:                  assert (false);
+              }
+            }
+          }
+
+          exec_lines (
+            g->tdown_.begin (), g->tdown_.end (), li, command_type::teardown);
+        }
+        else
+          assert (false);
+
+        runner_->leave (*scope_, scope_->end_loc_);
+
+        scope_->state = scope_state::passed;
+      }
+
+      bool parser::
+      exec_lines (lines::iterator i, lines::iterator e,
+                  size_t& li,
+                  command_type ct)
+      {
+        try
+        {
+          token t;
+          type tt;
+
+          for (; i != e; ++i)
+          {
+            line& ln (*i);
+            line_type lt (ln.type);
+
+            assert (path_ == nullptr);
+
+            // Set the tokens and start playing.
+            //
+            replay_data (move (ln.tokens));
+
+            // We don't really need to change the mode since we already know
+            // the line type.
+            //
+            next (t, tt);
+            const location ll (get_location (t));
+
+            switch (lt)
+            {
+            case line_type::var:
+              {
+                // Parse.
+                //
+                string name (move (t.value));
+
+                next (t, tt);
+                type kind (tt); // Assignment kind.
+
+                value rhs (parse_variable_line (t, tt));
+
+                if (tt == type::semi)
+                  next (t, tt);
+
+                assert (tt == type::newline);
+
+                // Assign.
+                //
+                const variable& var (*ln.var);
+
+                value& lhs (kind == type::assign
+                            ? scope_->assign (var)
+                            : scope_->append (var));
+
+                build2::parser::apply_value_attributes (
+                  &var, lhs, move (rhs), kind);
+
+                // If we changes any of the test.* values, then reset the $*,
+                // $N special aliases.
+                //
+                if (var.name == script_->test_var.name      ||
+                    var.name == script_->options_var.name   ||
+                    var.name == script_->arguments_var.name ||
+                    var.name == script_->redirects_var.name ||
+                    var.name == script_->cleanups_var.name)
+                {
+                  scope_->reset_special ();
+                }
+
+                replay_stop ();
+                break;
+              }
+            case line_type::cmd:
+              {
+                // We use the 0 index to signal that this is the only command.
+                // Note that we only do this for test commands.
+                //
+                if (ct == command_type::test && li == 0)
+                {
+                  lines::iterator j (i);
+                  for (++j; j != e && j->type == line_type::var; ++j) ;
+
+                  if (j != e) // We have another command.
+                    ++li;
+                }
+                else
+                  ++li;
+
+                command_expr ce (parse_command_line (t, tt));
+                runner_->run (*scope_, ce, ct, li, ll);
+
+                replay_stop ();
+                break;
+              }
+            case line_type::cmd_if:
+            case line_type::cmd_ifn:
+            case line_type::cmd_elif:
+            case line_type::cmd_elifn:
+            case line_type::cmd_else:
+              {
+                next (t, tt); // Skip to start of command.
+
+                bool take;
+                if (lt != line_type::cmd_else)
+                {
+                  // Assume if-else always involves multiple commands.
+                  //
+                  command_expr ce (parse_command_line (t, tt));
+                  take = runner_->run_if (*scope_, ce, ++li, ll);
+
+                  if (lt == line_type::cmd_ifn || lt == line_type::cmd_elifn)
+                    take = !take;
+                }
+                else
+                {
+                  assert (tt == type::newline);
+                  take = true;
+                }
+
+                replay_stop ();
+
+                // If end is true, then find the 'end' line. Otherwise, find
+                // the next if-else line. If skip is true then increment the
+                // command line index.
+                //
+                auto next = [e, &li]
+                  (lines::iterator j, bool end, bool skip) -> lines::iterator
+                  {
+                    // We need to be aware of nested if-else chains.
+                    //
+                    size_t n (0);
+
+                    for (++j; j != e; ++j)
+                    {
+                      line_type lt (j->type);
+
+                      if (lt == line_type::cmd_if ||
+                          lt == line_type::cmd_ifn)
+                        ++n;
+
+                      // If we are nested then we just wait until we get back
+                      // to the surface.
+                      //
+                      if (n == 0)
+                      {
+                        switch (lt)
+                        {
+                        case line_type::cmd_elif:
+                        case line_type::cmd_elifn:
+                        case line_type::cmd_else:
+                          if (end) break;
+                          // Fall through.
+                        case line_type::cmd_end:  return j;
+                        default: break;
+                        }
+                      }
+
+                      if (lt == line_type::cmd_end)
+                        --n;
+
+                      if (skip)
+                      {
+                        // Note that we don't count else and end as commands.
+                        //
+                        switch (lt)
+                        {
+                        case line_type::cmd:
+                        case line_type::cmd_if:
+                        case line_type::cmd_ifn:
+                        case line_type::cmd_elif:
+                        case line_type::cmd_elifn: ++li; break;
+                        default:                         break;
+                        }
+                      }
+                    }
+
+                    assert (false); // Missing end.
+                    return e;
+                  };
+
+                // If we are taking this branch then we need to parse all the
+                // lines until the next if-else line and then skip all the
+                // lines until the end (unless next is already end).
+                //
+                // Otherwise, we need to skip all the lines until the next
+                // if-else line and then continue parsing.
+                //
+                if (take)
+                {
+                  lines::iterator j (next (i, false, false)); // Next if-else.
+                  if (!exec_lines (i + 1, j, li, ct))
+                    return false;
+
+                  i = j->type == line_type::cmd_end ? j : next (j, true, true);
+                }
+                else
+                {
+                  i = next (i, false, true);
+                  if (i->type != line_type::cmd_end)
+                    --i; // Continue with this line (e.g., elif or else).
+                }
+
+                break;
+              }
+            case line_type::cmd_end:
+              {
+                assert (false);
+              }
+            }
+          }
+
+          return true;
+        }
+        catch (const exit_scope& e)
+        {
+          // Bail out if the scope is exited with the failure status. Otherwise
+          // leave the scope normally.
+          //
+          if (!e.status)
+            throw failed ();
+
+          replay_stop ();
+          return false;
+        }
+      }
+
+      //
+      // The rest.
+      //
+
+      lookup parser::
+      lookup_variable (name&& qual, string&& name, const location& loc)
+      {
+        assert (!pre_parse_);
+
+        if (!qual.empty ())
+          fail (loc) << "qualified variable name";
+
+        // If we have no scope (happens when pre-parsing directives), then we
+        // only look for buildfile variables.
+        //
+        // Otherwise, every variable that is ever set in a script has been
+        // pre-entered during pre-parse or introduced with the set builtin
+        // during test execution. Which means that if one is not found in the
+        // script pool then it can only possibly be set in the buildfile.
+        //
+        // Note that we need to acquire the variable pool lock. The pool can
+        // be changed from multiple threads by the set builtin. The obtained
+        // variable pointer can safelly be used with no locking as the variable
+        // pool is an associative container (underneath) and we are only adding
+        // new variables into it.
+        //
+        const variable* pvar (nullptr);
+
+        if (scope_ != nullptr)
+        {
+          slock sl (script_->var_pool_mutex);
+          pvar = script_->var_pool.find (name);
+        }
+
+        return pvar != nullptr
+          ? scope_->find (*pvar)
+          : script_->find_in_buildfile (name);
+      }
+
+      size_t parser::
+      quoted () const
+      {
+        size_t r (0);
+
+        if (replay_ != replay::play)
+          r = lexer_->quoted ();
+        else
+        {
+          // Examine tokens we have replayed since last reset.
+          //
+          for (size_t i (replay_quoted_); i != replay_i_; ++i)
+            if (replay_data_[i].token.qtype != quote_type::unquoted)
+              ++r;
+        }
+
+        return r;
+      }
+
+      void parser::
+      reset_quoted (token& cur)
+      {
+        if (replay_ != replay::play)
+          lexer_->reset_quoted (cur.qtype != quote_type::unquoted ? 1 : 0);
+        else
+        {
+          replay_quoted_ = replay_i_ - 1;
+
+          // Must be the same token.
+          //
+          assert (replay_data_[replay_quoted_].token.qtype == cur.qtype);
+        }
+      }
+
+      const string& parser::
+      insert_id (string id, location l)
+      {
+        auto p (id_map_->emplace (move (id), move (l)));
+
+        if (!p.second)
+          fail (l) << "duplicate id " << p.first->first <<
+            info (p.first->second) << "previously used here";
+
+        return p.first->first;
+      }
+
+      void parser::
+      set_lexer (lexer* l)
+      {
+        lexer_ = l;
+        base_parser::lexer_ = l;
+      }
+
+      void parser::
+      apply_value_attributes (const variable* var,
+                              value& lhs,
+                              value&& rhs,
+                              const string& attributes,
+                              token_type kind,
+                              const path& name)
+      {
+        path_ = &name;
+
+        istringstream is (attributes);
+        lexer l (is, name, lexer_mode::attribute);
+        set_lexer (&l);
+
+        token t;
+        type tt;
+        next (t, tt);
+
+        if (tt != type::lsbrace && tt != type::eos)
+          fail (t) << "expected '[' instead of " << t;
+
+        attributes_push (t, tt, true);
+
+        if (tt != type::eos)
+          fail (t) << "trailing junk after ']'";
+
+        build2::parser::apply_value_attributes (var, lhs, move (rhs), kind);
+      }
+
+      // parser::parsed_doc
+      //
+      parser::parsed_doc::
+      parsed_doc (string s, uint64_t l, uint64_t c)
+          : str (move (s)), re (false), end_line (l), end_column (c)
+      {
+      }
+
+      parser::parsed_doc::
+      parsed_doc (regex_lines&& r, uint64_t l, uint64_t c)
+          : regex (move (r)), re (true), end_line (l), end_column (c)
+      {
+      }
+
+      parser::parsed_doc::
+      parsed_doc (parsed_doc&& d)
+          : re (d.re), end_line (d.end_line), end_column (d.end_column)
+      {
+        if (re)
+          new (&regex) regex_lines (move (d.regex));
+        else
+          new (&str) string (move (d.str));
+      }
+
+      parser::parsed_doc::
+      ~parsed_doc ()
+      {
+        if (re)
+          regex.~regex_lines ();
+        else
+          str.~string ();
+      }
+    }
+  }
+}
diff --git a/libbuild2/test/script/parser.hxx b/libbuild2/test/script/parser.hxx
new file mode 100644
index 0000000..1beee49
--- /dev/null
+++ b/libbuild2/test/script/parser.hxx
@@ -0,0 +1,250 @@
+// file      : libbuild2/test/script/parser.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_TEST_SCRIPT_PARSER_HXX
+#define LIBBUILD2_TEST_SCRIPT_PARSER_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/parser.hxx>
+#include <libbuild2/diagnostics.hxx>
+
+#include <libbuild2/test/script/token.hxx>
+#include <libbuild2/test/script/script.hxx>
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      class lexer;
+      class runner;
+
+      class parser: protected build2::parser
+      {
+        // Pre-parse. Issue diagnostics and throw failed in case of an error.
+        //
+      public:
+        void
+        pre_parse (script&);
+
+        void
+        pre_parse (istream&, script&);
+
+        // Helpers.
+        //
+        // Parse attribute string and perform attribute-guided assignment.
+        // Issue diagnostics and throw failed in case of an error.
+        //
+        void
+        apply_value_attributes (const variable*, // Optional.
+                                value& lhs,
+                                value&& rhs,
+                                const string& attributes,
+                                token_type assign_kind,
+                                const path& name); // For diagnostics.
+
+        // Recursive descent parser.
+        //
+        // Usually (but not always) parse functions receive the token/type
+        // from which it should start consuming and in return the token/type
+        // should contain the first token that has not been consumed.
+        //
+        // Functions that are called parse_*() rather than pre_parse_*() are
+        // used for both stages.
+        //
+      protected:
+        bool
+        pre_parse_demote_group_scope (unique_ptr<scope>&);
+
+        token
+        pre_parse_scope_body ();
+
+        unique_ptr<group>
+        pre_parse_scope_block (token&, token_type&, const string&);
+
+        bool
+        pre_parse_line (token&, token_type&,
+                        optional<description>&,
+                        lines* = nullptr,
+                        bool one = false);
+
+        bool
+        pre_parse_if_else (token&, token_type&,
+                           optional<description>&,
+                           lines&);
+
+        bool
+        pre_parse_if_else_scope (token&, token_type&,
+                                 optional<description>&,
+                                 lines&);
+
+        bool
+        pre_parse_if_else_command (token&, token_type&,
+                                   optional<description>&,
+                                   lines&);
+
+        void
+        pre_parse_directive (token&, token_type&);
+
+        void
+        pre_parse_include_line (names, location);
+
+        description
+        pre_parse_leading_description (token&, token_type&);
+
+        description
+        parse_trailing_description (token&, token_type&);
+
+        value
+        parse_variable_line (token&, token_type&);
+
+        command_expr
+        parse_command_line (token&, token_type&);
+
+        // Ordered sequence of here-document redirects that we can expect to
+        // see after the command line.
+        //
+        struct here_redirect
+        {
+          size_t expr; // Index in command_expr.
+          size_t pipe; // Index in command_pipe.
+          int fd;      // Redirect fd (0 - in, 1 - out, 2 - err).
+        };
+
+        struct here_doc
+        {
+          // Redirects that share here_doc. Most of the time we will have no
+          // more than 2 (2 - for the roundtrip test cases).
+          //
+          small_vector<here_redirect, 2> redirects;
+
+          string end;
+          bool literal;     // Literal (single-quote).
+          string modifiers;
+
+          // Regex introducer ('\0' if not a regex, so can be used as bool).
+          //
+          char regex;
+
+          // Regex global flags. Meaningful if regex != '\0'.
+          //
+          string regex_flags;
+        };
+        using here_docs = vector<here_doc>;
+
+        pair<command_expr, here_docs>
+        parse_command_expr (token&, token_type&);
+
+        command_exit
+        parse_command_exit (token&, token_type&);
+
+        void
+        parse_here_documents (token&, token_type&,
+                              pair<command_expr, here_docs>&);
+
+        struct parsed_doc
+        {
+          union
+          {
+            string str;        // Here-document literal.
+            regex_lines regex; // Here-document regex.
+          };
+
+          bool re;             // True if regex.
+          uint64_t end_line;   // Here-document end marker location.
+          uint64_t end_column;
+
+          parsed_doc (string, uint64_t line, uint64_t column);
+          parsed_doc (regex_lines&&, uint64_t line, uint64_t column);
+          parsed_doc (parsed_doc&&); // Note: move constuctible-only type.
+          ~parsed_doc ();
+        };
+
+        parsed_doc
+        parse_here_document (token&, token_type&,
+                             const string&,
+                             const string& mode,
+                             char re_intro);      // '\0' if not a regex.
+
+        // Execute. Issue diagnostics and throw failed in case of an error.
+        //
+      public:
+        void
+        execute (script& s, runner& r);
+
+        void
+        execute (scope&, script&, runner&);
+
+      protected:
+        void
+        exec_scope_body ();
+
+        // Return false if the execution of the scope should be terminated
+        // with the success status (e.g., as a result of encountering the exit
+        // builtin). For unsuccessful termination the failed exception should
+        // be thrown.
+        //
+        bool
+        exec_lines (lines::iterator, lines::iterator, size_t&, command_type);
+
+        // Customization hooks.
+        //
+      protected:
+        virtual lookup
+        lookup_variable (name&&, string&&, const location&) override;
+
+        // Number of quoted tokens since last reset. Note that this includes
+        // the peeked token, if any.
+        //
+      protected:
+        size_t
+        quoted () const;
+
+        void
+        reset_quoted (token& current);
+
+        size_t replay_quoted_;
+
+        // Insert id into the id map checking for duplicates.
+        //
+      protected:
+        const string&
+        insert_id (string, location);
+
+        // Set lexer pointers for both the current and the base classes.
+        //
+      protected:
+        void
+        set_lexer (lexer* l);
+
+      protected:
+        using base_parser = build2::parser;
+
+        script* script_;
+
+        // Pre-parse state.
+        //
+        using id_map = std::unordered_map<string, location>;
+        using include_set = std::set<path>;
+
+        group* group_;
+        id_map* id_map_;
+        include_set* include_set_; // Testscripts already included in this
+                                   // scope. Must be absolute and normalized.
+        lexer* lexer_;
+        string id_prefix_; // Auto-derived id prefix.
+
+        // Execute state.
+        //
+        runner* runner_;
+        scope* scope_;
+      };
+    }
+  }
+}
+
+#endif // LIBBUILD2_TEST_SCRIPT_PARSER_HXX
diff --git a/libbuild2/test/script/parser.test.cxx b/libbuild2/test/script/parser.test.cxx
new file mode 100644
index 0000000..8702e18
--- /dev/null
+++ b/libbuild2/test/script/parser.test.cxx
@@ -0,0 +1,245 @@
+// file      : libbuild2/test/script/parser.test.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <cassert>
+#include <iostream>
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/target.hxx>
+#include <libbuild2/context.hxx>   // reset()
+#include <libbuild2/scheduler.hxx>
+
+#include <libbuild2/test/target.hxx>
+
+#include <libbuild2/test/script/token.hxx>
+#include <libbuild2/test/script/parser.hxx>
+#include <libbuild2/test/script/runner.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      // Here we assume we are running serially.
+      //
+      class print_runner: public runner
+      {
+      public:
+        print_runner (bool scope, bool id, bool line)
+            : scope_ (scope), id_ (id), line_ (line) {}
+
+        virtual bool
+        test (scope&) const override
+        {
+          return true;
+        }
+
+        virtual void
+        enter (scope& s, const location&) override
+        {
+          if (s.desc)
+          {
+            const auto& d (*s.desc);
+
+            if (!d.id.empty ())
+              cout << ind_ << ": id:" << d.id << endl;
+
+            if (!d.summary.empty ())
+              cout << ind_ << ": sm:" << d.summary << endl;
+
+            if (!d.details.empty ())
+            {
+              if (!d.id.empty () || !d.summary.empty ())
+                cout << ind_ << ":" << endl; // Blank.
+
+              const auto& s (d.details);
+              for (size_t b (0), e (0), n; e != string::npos; b = e + 1)
+              {
+                e = s.find ('\n', b);
+                n = ((e != string::npos ? e : s.size ()) - b);
+
+                cout << ind_ << ':';
+                if (n != 0)
+                {
+                  cout << ' ';
+                  cout.write (s.c_str () + b, static_cast<streamsize> (n));
+                }
+                cout << endl;
+              }
+            }
+          }
+
+          if (scope_)
+          {
+            cout << ind_ << "{";
+
+            if (id_ && !s.id_path.empty ()) // Skip empty root scope id.
+              cout << " # " << s.id_path.string ();
+
+            cout << endl;
+
+            ind_ += "  ";
+          }
+        }
+
+        virtual void
+        run (scope&,
+             const command_expr& e, command_type t,
+             size_t i,
+             const location&) override
+        {
+          const char* s (nullptr);
+
+          switch (t)
+          {
+          case command_type::test:     s = "";  break;
+          case command_type::setup:    s = "+"; break;
+          case command_type::teardown: s = "-"; break;
+          }
+
+          cout << ind_ << s << e;
+
+          if (line_)
+            cout << " # " << i;
+
+          cout << endl;
+        }
+
+        virtual bool
+        run_if (scope&,
+                const command_expr& e,
+                size_t i,
+                const location&) override
+        {
+          cout << ind_ << "? " << e;
+
+          if (line_)
+            cout << " # " << i;
+
+          cout << endl;
+
+          return e.back ().pipe.back ().program.string () == "true";
+        }
+
+        virtual void
+        leave (scope&, const location&) override
+        {
+          if (scope_)
+          {
+            ind_.resize (ind_.size () - 2);
+            cout << ind_ << "}" << endl;
+          }
+        }
+
+      private:
+        bool scope_;
+        bool id_;
+        bool line_;
+        string ind_;
+      };
+
+      // Usage: argv[0] [-s] [-i] [-l] [<testscript-name>]
+      //
+      int
+      main (int argc, char* argv[])
+      {
+        tracer trace ("main");
+
+        // Fake build system driver, default verbosity.
+        //
+        init_diag (1);
+        init (argv[0]);
+        sched.startup (1);  // Serial execution.
+        reset (strings ()); // No command line variables.
+
+        bool scope (false);
+        bool id (false);
+        bool line (false);
+        path name;
+
+        for (int i (1); i != argc; ++i)
+        {
+          string a (argv[i]);
+
+          if (a == "-s")
+            scope = true;
+          else if (a == "-i")
+            id = true;
+          else if (a == "-l")
+            line = true;
+          else
+          {
+            name = path (move (a));
+            break;
+          }
+        }
+
+        if (name.empty ())
+          name = path ("testscript");
+
+        assert (!id || scope); // Id can only be printed with scope.
+
+        try
+        {
+          cin.exceptions (istream::failbit | istream::badbit);
+
+          // Enter mock targets. Use fixed names and paths so that we can use
+          // them in expected results. Strictly speaking target paths should
+          // be absolute. However, the testscript implementation doesn't
+          // really care.
+          //
+          file& tt (
+            targets.insert<file> (work,
+                                  dir_path (),
+                                  "driver",
+                                  string (),
+                                  trace));
+
+          value& v (
+            tt.assign (
+              var_pool.rw ().insert<target_triplet> (
+                "test.target", variable_visibility::project)));
+
+          v = cast<target_triplet> ((*global_scope)["build.host"]);
+
+          testscript& st (
+            targets.insert<testscript> (work,
+                                        dir_path (),
+                                        name.leaf ().base ().string (),
+                                        name.leaf ().extension (),
+                                        trace));
+
+          tt.path (path ("driver"));
+          st.path (name);
+
+          // Parse and run.
+          //
+          parser p;
+          script s (tt, st, dir_path (work) /= "test-driver");
+          p.pre_parse (cin, s);
+
+          print_runner r (scope, id, line);
+          p.execute (s, r);
+        }
+        catch (const failed&)
+        {
+          return 1;
+        }
+
+        return 0;
+      }
+    }
+  }
+}
+
+int
+main (int argc, char* argv[])
+{
+  return build2::test::script::main (argc, argv);
+}
diff --git a/libbuild2/test/script/regex.cxx b/libbuild2/test/script/regex.cxx
new file mode 100644
index 0000000..20dfaa6
--- /dev/null
+++ b/libbuild2/test/script/regex.cxx
@@ -0,0 +1,440 @@
+// file      : libbuild2/test/script/regex.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <locale>
+
+#include <libbuild2/test/script/regex.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      namespace regex
+      {
+        static_assert (alignof (char_string) % 4 == 0,
+                       "unexpected char_string alignment");
+
+        static_assert (alignof (char_regex) % 4 == 0,
+                       "unexpected char_regex alignment");
+
+        static_assert (sizeof (uintptr_t) > sizeof (int16_t),
+                       "unexpected uintptr_t size");
+
+        const line_char line_char::nul (0);
+        const line_char line_char::eof (-1);
+
+        // line_char
+        //
+        // We package the special character into uintptr_t with the following
+        // steps:
+        //
+        // - narrow down int value to int16_t (preserves all the valid values)
+        //
+        // - convert to uint16_t (bitwise representation stays the same, but no
+        //   need to bother with signed value widening, leftmost bits loss on
+        //   left shift, etc)
+        //
+        // - convert to uintptr_t (storage type)
+        //
+        // - shift left by two bits (the operation is fully reversible as
+        //   uintptr_t is wider then uint16_t)
+        //
+        line_char::
+        line_char (int c)
+            : data_ (
+              (static_cast <uintptr_t> (
+                static_cast<uint16_t> (
+                  static_cast<int16_t> (c))) << 2) |
+              static_cast <uintptr_t> (line_type::special))
+        {
+          // @@ How can we allow anything for basic_regex but only subset
+          //    for our own code?
+          //
+          const char ex[] = "pn\n\r";
+
+          assert (c == 0  || // Null character.
+
+                  // EOF. Note that is also passed by msvcrt as _Meta_eos
+                  // enum value.
+                  //
+                  c == -1 ||
+
+                  // libstdc++ line/paragraph separators.
+                  //
+                  c == u'\u2028' || c == u'\u2029' ||
+
+                  (c > 0 && c <= 255 && (
+                    // Supported regex special characters.
+                    //
+                    syntax (c) ||
+
+                    // libstdc++ look-ahead tokens, newline chars.
+                    //
+                    string::traits_type::find (ex, 4, c) != nullptr)));
+        }
+
+        line_char::
+        line_char (const char_string& s, line_pool& p)
+            : line_char (&(*p.strings.emplace (s).first))
+        {
+        }
+
+        line_char::
+        line_char (char_string&& s, line_pool& p)
+            : line_char (&(*p.strings.emplace (move (s)).first))
+        {
+        }
+
+        line_char::
+        line_char (char_regex r, line_pool& p)
+            // Note: in C++17 can write as p.regexes.emplace_front(move (r))
+            //
+            : line_char (&(*p.regexes.emplace (p.regexes.begin (), move (r))))
+        {
+        }
+
+        bool
+        line_char::syntax (char c)
+        {
+          return string::traits_type::find (
+            "()|.*+?{}\\0123456789,=!", 23, c) != nullptr;
+        }
+
+        bool
+        operator== (const line_char& l, const line_char& r)
+        {
+          line_type lt (l.type ());
+          line_type rt (r.type ());
+
+          if (lt == rt)
+          {
+            bool res (true);
+
+            switch (lt)
+            {
+            case line_type::special: res = l.special () == r.special (); break;
+            case line_type::regex:   assert (false); break;
+
+              // Note that we use pointers (rather than vales) comparison
+              // assuming that the strings must belong to the same pool.
+              //
+            case line_type::literal: res = l.literal () == r.literal (); break;
+            }
+
+            return res;
+          }
+
+          // Match literal with regex.
+          //
+          if (lt == line_type::literal && rt == line_type::regex)
+            return regex_match (*l.literal (), *r.regex ());
+          else if (rt == line_type::literal && lt == line_type::regex)
+            return regex_match (*r.literal (), *l.regex ());
+
+          return false;
+        }
+
+        bool
+        operator< (const line_char& l, const line_char& r)
+        {
+          if (l == r)
+            return false;
+
+          line_type lt (l.type ());
+          line_type rt (r.type ());
+
+          if (lt != rt)
+            return lt < rt;
+
+          bool res (false);
+
+          switch (lt)
+          {
+          case line_type::special: res =  l.special () <  r.special (); break;
+          case line_type::literal: res = *l.literal () < *r.literal (); break;
+          case line_type::regex:   assert (false); break;
+          }
+
+          return res;
+        }
+
+        // line_char_locale
+        //
+
+        // An exemplar locale with the std::ctype<line_char> facet. It is used
+        // for the subsequent line char locale objects creation (see below)
+        // which normally ends up with a shallow copy of a reference-counted
+        // object.
+        //
+        // Note that creating the line char locales from the exemplar is not
+        // merely an optimization: there is a data race in the libstdc++ (at
+        // least as of GCC 9.1) implementation of the locale(const locale&,
+        // Facet*) constructor (bug #91057).
+        //
+        // Also note that we install the facet in init() rather than during
+        // the object creation to avoid a race with the std::locale-related
+        // global variables initialization.
+        //
+        static locale line_char_locale_exemplar;
+
+        void
+        init ()
+        {
+          line_char_locale_exemplar =
+            locale (locale (),
+                    new std::ctype<line_char> ()); // Hidden by ctype bitmask.
+        }
+
+        line_char_locale::
+        line_char_locale ()
+            : locale (line_char_locale_exemplar)
+        {
+          // Make sure init() has been called.
+          //
+          // Note: has_facet() is hidden by a private function in libc++.
+          //
+          assert (std::has_facet<std::ctype<line_char>> (*this));
+        }
+
+        // char_regex
+        //
+        // Transform regex according to the extended flags {idot}. If regex is
+        // malformed then keep transforming, so the resulting string is
+        // malformed the same way. We expect the error to be reported by the
+        // char_regex ctor.
+        //
+        static string
+        transform (const string& s, char_flags f)
+        {
+          assert ((f & char_flags::idot) != char_flags::none);
+
+          string r;
+          bool escape (false);
+          bool cclass (false);
+
+          for (char c: s)
+          {
+            // Inverse escaping for a dot which is out of the char class
+            // brackets.
+            //
+            bool inverse (c == '.' && !cclass);
+
+            // Handle the escape case. Note that we delay adding the backslash
+            // since we may have to inverse things.
+            //
+            if (escape)
+            {
+              if (!inverse)
+                r += '\\';
+
+              r += c;
+              escape = false;
+
+              continue;
+            }
+            else if (c == '\\')
+            {
+              escape = true;
+              continue;
+            }
+
+            // Keep track of being inside the char class brackets, escape if
+            // inversion. Note that we never inverse square brackets.
+            //
+            if (c == '[' && !cclass)
+              cclass = true;
+            else if (c == ']' && cclass)
+              cclass = false;
+            else if (inverse)
+              r += '\\';
+
+            r += c;
+          }
+
+          if (escape) // Regex is malformed but that's not our problem.
+            r += '\\';
+
+          return r;
+        }
+
+        static char_regex::flag_type
+        to_std_flags (char_flags f)
+        {
+          // Note that ECMAScript flag is implied in the absense of a grammar
+          // flag.
+          //
+          return (f & char_flags::icase) != char_flags::none
+            ? char_regex::icase
+            : char_regex::flag_type ();
+        }
+
+        char_regex::
+        char_regex (const char_string& s, char_flags f)
+            : base_type ((f & char_flags::idot) != char_flags::none
+                         ? transform (s, f)
+                         : s,
+                         to_std_flags (f))
+        {
+        }
+      }
+    }
+  }
+}
+
+namespace std
+{
+  using namespace build2::test::script::regex;
+
+  // char_traits<line_char>
+  //
+  line_char* char_traits<line_char>::
+  assign (char_type* s, size_t n, char_type c)
+  {
+    for (size_t i (0); i != n; ++i)
+      s[i] = c;
+    return s;
+  }
+
+  line_char* char_traits<line_char>::
+  move (char_type* d, const char_type* s, size_t n)
+  {
+    if (n > 0 && d != s)
+    {
+      // If d < s then it can't be in [s, s + n) range and so using copy() is
+      // safe. Otherwise d + n is out of (s, s + n] range and so using
+      // copy_backward() is safe.
+      //
+      if (d < s)
+        std::copy (s, s + n, d); // Hidden by char_traits<line_char>::copy().
+      else
+        copy_backward (s, s + n, d + n);
+    }
+
+    return d;
+  }
+
+  line_char* char_traits<line_char>::
+  copy (char_type* d, const char_type* s, size_t n)
+  {
+    std::copy (s, s + n, d); // Hidden by char_traits<line_char>::copy().
+    return d;
+  }
+
+  int char_traits<line_char>::
+  compare (const char_type* s1, const char_type* s2, size_t n)
+  {
+    for (size_t i (0); i != n; ++i)
+    {
+      if (s1[i] < s2[i])
+        return -1;
+      else if (s2[i] < s1[i])
+        return 1;
+    }
+
+    return 0;
+  }
+
+  size_t char_traits<line_char>::
+  length (const char_type* s)
+  {
+    size_t i (0);
+    while (s[i] != char_type::nul)
+      ++i;
+
+    return i;
+  }
+
+  const line_char* char_traits<line_char>::
+  find (const char_type* s, size_t n, const char_type& c)
+  {
+    for (size_t i (0); i != n; ++i)
+    {
+      if (s[i] == c)
+        return s + i;
+    }
+
+    return nullptr;
+  }
+
+  // ctype<line_char>
+  //
+  locale::id ctype<line_char>::id;
+
+  const line_char* ctype<line_char>::
+  is (const char_type* b, const char_type* e, mask* m) const
+  {
+    while (b != e)
+    {
+      const char_type& c (*b++);
+
+      *m++ = c.type () == line_type::special && c.special () >= 0 &&
+        build2::digit (static_cast<char> (c.special ()))
+        ? digit
+        : 0;
+    }
+
+    return e;
+  }
+
+  const line_char* ctype<line_char>::
+  scan_is (mask m, const char_type* b, const char_type* e) const
+  {
+    for (; b != e; ++b)
+    {
+      if (is (m, *b))
+        return b;
+    }
+
+    return e;
+  }
+
+  const line_char* ctype<line_char>::
+  scan_not (mask m, const char_type* b, const char_type* e) const
+  {
+    for (; b != e; ++b)
+    {
+      if (!is (m, *b))
+        return b;
+    }
+
+    return e;
+  }
+
+  const char* ctype<line_char>::
+  widen (const char* b, const char* e, char_type* c) const
+  {
+    while (b != e)
+      *c++ = widen (*b++);
+
+    return e;
+  }
+
+  const line_char* ctype<line_char>::
+  narrow (const char_type* b, const char_type* e, char def, char* c) const
+  {
+    while (b != e)
+      *c++ = narrow (*b++, def);
+
+    return e;
+  }
+
+  // regex_traits<line_char>
+  //
+  int regex_traits<line_char>::
+  value (char_type c, int radix) const
+  {
+    assert (radix == 8 || radix == 10 || radix == 16);
+
+    if (c.type () != line_type::special)
+      return -1;
+
+    const char digits[] = "0123456789ABCDEF";
+    const char* d (string::traits_type::find (digits, radix, c.special ()));
+    return d != nullptr ? static_cast<int> (d - digits) : -1;
+  }
+}
diff --git a/libbuild2/test/script/regex.hxx b/libbuild2/test/script/regex.hxx
new file mode 100644
index 0000000..faec1fc
--- /dev/null
+++ b/libbuild2/test/script/regex.hxx
@@ -0,0 +1,703 @@
+// file      : libbuild2/test/script/regex.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_TEST_SCRIPT_REGEX_HXX
+#define LIBBUILD2_TEST_SCRIPT_REGEX_HXX
+
+#include <list>
+#include <regex>
+#include <locale>
+#include <string>        // basic_string
+#include <type_traits>   // make_unsigned, enable_if, is_*
+#include <unordered_set>
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      namespace regex
+      {
+        using char_string = std::basic_string<char>;
+
+        enum class char_flags: uint16_t
+        {
+          icase = 0x1, // Case-insensitive match.
+          idot  = 0x2, // Invert '.' escaping.
+
+          none = 0
+        };
+
+        // Restricts valid standard flags to just {icase}, extends with custom
+        // flags {idot}.
+        //
+        class char_regex: public std::basic_regex<char>
+        {
+        public:
+          using base_type = std::basic_regex<char>;
+
+          char_regex (const char_string&, char_flags = char_flags::none);
+        };
+
+        // Newlines are line separators and are not part of the line:
+        //
+        // line<newline>line<newline>
+        //
+        // Specifically, this means that a customary trailing newline creates a
+        // trailing blank line.
+        //
+        // All characters can inter-compare (though there cannot be regex
+        // characters in the output, only in line_regex).
+        //
+        // Note that we assume that line_regex and the input to regex_match()
+        // use the same pool.
+        //
+        struct line_pool
+        {
+          // Note that we assume the pool can be moved without invalidating
+          // pointers to any already pooled entities.
+          //
+          std::unordered_set<char_string> strings;
+          std::list<char_regex> regexes;
+        };
+
+        enum class line_type
+        {
+          special,
+          literal,
+          regex
+        };
+
+        struct line_char
+        {
+          // Steal last two bits from the pointer to store the type.
+          //
+        private:
+          std::uintptr_t data_;
+
+        public:
+          line_type
+          type () const {return static_cast<line_type> (data_ & 0x3);}
+
+          int
+          special () const
+          {
+            // Stored as (shifted) int16_t. Perform steps reversed to those
+            // that are described in the comment for the corresponding ctor.
+            // Note that the intermediate cast to uint16_t is required to
+            // portably preserve the -1 special character.
+            //
+            return static_cast<int16_t> (static_cast<uint16_t> (data_ >> 2));
+          }
+
+          const char_string*
+          literal () const
+          {
+            // Note that 2 rightmost bits are used for packaging line_char
+            // type. Read the comment for the corresponding ctor for details.
+            //
+            return reinterpret_cast<const char_string*> (
+              data_ & ~std::uintptr_t (0x3));
+          }
+
+          const char_regex*
+          regex () const
+          {
+            // Note that 2 rightmost bits are used for packaging line_char
+            // type. Read the comment for the corresponding ctor for details.
+            //
+            return reinterpret_cast<const char_regex*> (
+              data_ & ~std::uintptr_t (0x3));
+          }
+
+          static const line_char nul;
+          static const line_char eof;
+
+          // Note: creates an uninitialized value.
+          //
+          line_char () = default;
+
+          // Create a special character. The argument value must be one of the
+          // following ones:
+          //
+          // 0 (nul character)
+          // -1 (EOF)
+          // [()|.*+?{}\0123456789,=!] (excluding [])
+          //
+          // Note that the constructor is implicit to allow basic_regex to
+          // implicitly construct line_chars from special char literals (in
+          // particular libstdc++ appends them to an internal line_string).
+          //
+          // Also note that we extend the valid characters set (see above) with
+          // 'p', 'n' (used by libstdc++ for positive/negative look-ahead
+          // tokens representation), and '\n', '\r', u'\u2028', u'\u2029' (used
+          // by libstdc++ for newline/newparagraph matching).
+          //
+          line_char (int);
+
+          // Create a literal character.
+          //
+          // Don't copy string if already pooled.
+          //
+          explicit
+          line_char (const char_string&, line_pool&);
+
+          explicit
+          line_char (char_string&&, line_pool&);
+
+          explicit
+          line_char (const char_string* s) // Assume already pooled.
+              //
+              // Steal two bits from the pointer to package line_char type.
+              // Assume (and statically assert) that char_string address is a
+              // multiple of four.
+              //
+              : data_ (reinterpret_cast <std::uintptr_t> (s) |
+                       static_cast <std::uintptr_t> (line_type::literal)) {}
+
+          // Create a regex character.
+          //
+          explicit
+          line_char (char_regex, line_pool&);
+
+          explicit
+          line_char (const char_regex* r) // Assume already pooled.
+              //
+              // Steal two bits from the pointer to package line_char type.
+              // Assume (and statically assert) that char_regex address is a
+              // multiple of four.
+              //
+              : data_ (reinterpret_cast <std::uintptr_t> (r) |
+                       static_cast <std::uintptr_t> (line_type::regex)) {}
+
+          // Provide basic_regex with the ability to use line_char in a context
+          // where a char value is expected (e.g., as a function argument).
+          //
+          // libstdc++ seems to cast special line_chars only (and such a
+          // conversion is meanigfull).
+          //
+          // msvcrt casts line_chars of arbitrary types instead. The only
+          // reasonable strategy is to return a value that differs from any
+          // other that can be encountered in a regex expression and so will
+          // unlikelly be misinterpreted.
+          //
+          operator char () const
+          {
+            return type () == line_type::special ? special () : '\a'; // BELL.
+          }
+
+          // Return true if the character is a syntax (special) one.
+          //
+          static bool
+          syntax (char);
+
+          // Provide basic_regex (such as from msvcrt) with the ability to
+          // explicitly cast line_chars to implementation-specific enums.
+          //
+          template <typename T>
+          explicit
+          operator T () const
+          {
+            assert (type () == line_type::special);
+            return static_cast<T> (special ());
+          }
+        };
+
+        // Perform "deep" characters comparison (for example match literal
+        // character with a regex character), rather than just compare them
+        // literally. At least one argument must be of a type other than regex
+        // as there is no operator==() defined to compare regexes. Characters
+        // of the literal type must share the same pool (strings are compared
+        // by pointers not by values).
+        //
+        bool
+        operator== (const line_char&, const line_char&);
+
+        // Return false if arguments are equal (operator==() returns true).
+        // Otherwise if types are different return the value implying that
+        // special < literal < regex. If types are special or literal return
+        // the result of the respective characters or strings comparison. At
+        // least one argument must be of a type other than regex as there is no
+        // operator<() defined to compare regexes.
+        //
+        // While not very natural operation for the class we have, we have to
+        // provide some meaningfull semantics for such a comparison as it is
+        // required by the char_traits<line_char> specialization. While we
+        // could provide it right in that specialization, let's keep it here
+        // for basic_regex implementations that potentially can compare
+        // line_chars as they compare them with expressions of other types (see
+        // below).
+        //
+        bool
+        operator< (const line_char&, const line_char&);
+
+        inline bool
+        operator!= (const line_char& l, const line_char& r)
+        {
+          return !(l == r);
+        }
+
+        inline bool
+        operator<= (const line_char& l, const line_char& r)
+        {
+          return l < r || l == r;
+        }
+
+        // Provide basic_regex (such as from msvcrt) with the ability to
+        // compare line_char to a value of an integral or
+        // implementation-specific enum type. In the absense of the following
+        // template operators, such a comparisons would be ambigious for
+        // integral types (given that there are implicit conversions
+        // int->line_char and line_char->char) and impossible for enums.
+        //
+        // Note that these == and < operators can succeed only for a line_char
+        // of the special type. For other types they always return false. That
+        // in particular leads to the following case:
+        //
+        // (lc != c) != (lc < c || c < lc).
+        //
+        // Note that we can not assert line_char is of the special type as
+        // basic_regex (such as from libc++) may need the ability to check if
+        // arbitrary line_char belongs to some special characters range (like
+        // ['0', '9']).
+        //
+        template <typename T>
+        struct line_char_cmp
+          : public std::enable_if<std::is_integral<T>::value ||
+                                  (std::is_enum<T>::value &&
+                                   !std::is_same<T, char_flags>::value)> {};
+
+        template <typename T, typename = typename line_char_cmp<T>::type>
+        bool
+        operator== (const line_char& l, const T& r)
+        {
+          return l.type () == line_type::special &&
+            static_cast<T> (l.special ()) == r;
+        }
+
+        template <typename T, typename = typename line_char_cmp<T>::type>
+        bool
+        operator== (const T& l, const line_char& r)
+        {
+          return r.type () == line_type::special &&
+            static_cast<T> (r.special ()) == l;
+        }
+
+        template <typename T, typename = typename line_char_cmp<T>::type>
+        bool
+        operator!= (const line_char& l, const T& r)
+        {
+          return !(l == r);
+        }
+
+        template <typename T, typename = typename line_char_cmp<T>::type>
+        bool
+        operator!= (const T& l, const line_char& r)
+        {
+          return !(l == r);
+        }
+
+        template <typename T, typename = typename line_char_cmp<T>::type>
+        bool
+        operator< (const line_char& l, const T& r)
+        {
+          return l.type () == line_type::special &&
+            static_cast<T> (l.special ()) < r;
+        }
+
+        template <typename T, typename = typename line_char_cmp<T>::type>
+        bool
+        operator< (const T& l, const line_char& r)
+        {
+          return r.type () == line_type::special &&
+            l < static_cast<T> (r.special ());
+        }
+
+        template <typename T, typename = typename line_char_cmp<T>::type>
+        inline bool
+        operator<= (const line_char& l, const T& r)
+        {
+          return l < r || l == r;
+        }
+
+        template <typename T, typename = typename line_char_cmp<T>::type>
+        inline bool
+        operator<= (const T& l, const line_char& r)
+        {
+          return l < r || l == r;
+        }
+
+        using line_string = std::basic_string<line_char>;
+
+        // Locale that has ctype<line_char> facet installed. Used in the
+        // regex_traits<line_char> specialization (see below).
+        //
+        class line_char_locale: public std::locale
+        {
+        public:
+          // Create a copy of the global C++ locale.
+          //
+          line_char_locale ();
+        };
+
+        // Initialize the testscript regex global state. Should be called once
+        // prior to creating objects of types from this namespace. Note: not
+        // thread-safe.
+        //
+        void
+        init ();
+      }
+    }
+  }
+}
+
+// Standard template specializations for line_char that are required for the
+// basic_regex<line_char> instantiation.
+//
+namespace std
+{
+  template <>
+  class char_traits<build2::test::script::regex::line_char>
+  {
+  public:
+    using char_type  = build2::test::script::regex::line_char;
+    using int_type   = char_type;
+    using off_type   = char_traits<char>::off_type;
+    using pos_type   = char_traits<char>::pos_type;
+    using state_type = char_traits<char>::state_type;
+
+    static void
+    assign (char_type& c1, const char_type& c2) {c1 = c2;}
+
+    static char_type*
+    assign (char_type*, size_t, char_type);
+
+    // Note that eq() and lt() are not constexpr (as required by C++11)
+    // because == and < operators for char_type are not constexpr.
+    //
+    static bool
+    eq (const char_type& l, const char_type& r) {return l == r;}
+
+    static bool
+    lt (const char_type& l, const char_type& r) {return l < r;}
+
+    static char_type*
+    move (char_type*, const char_type*, size_t);
+
+    static char_type*
+    copy (char_type*, const char_type*, size_t);
+
+    static int
+    compare (const char_type*, const char_type*, size_t);
+
+    static size_t
+    length (const char_type*);
+
+    static const char_type*
+    find (const char_type*, size_t, const char_type&);
+
+    static constexpr char_type
+    to_char_type (const int_type& c) {return c;}
+
+    static constexpr int_type
+    to_int_type (const char_type& c) {return int_type (c);}
+
+    // Note that the following functions are not constexpr (as required by
+    // C++11) because their return expressions are not constexpr.
+    //
+    static bool
+    eq_int_type (const int_type& l, const int_type& r) {return l == r;}
+
+    static int_type eof () {return char_type::eof;}
+
+    static int_type
+    not_eof (const int_type& c)
+    {
+      return c != char_type::eof ? c : char_type::nul;
+    }
+  };
+
+  // ctype<> must be derived from both ctype_base and locale::facet (the later
+  // supports ref-counting used by the std::locale implementation internally).
+  //
+  // msvcrt for some reason also derives ctype_base from locale::facet which
+  // produces "already a base-class" warning and effectivelly breaks the
+  // reference counting. So we derive from ctype_base only in this case.
+  //
+  template <>
+  class ctype<build2::test::script::regex::line_char>: public ctype_base
+#if !defined(_MSC_VER) || _MSC_VER >= 2000
+                                              , public locale::facet
+#endif
+  {
+    // Used by the implementation only.
+    //
+    using line_type = build2::test::script::regex::line_type;
+
+  public:
+    using char_type = build2::test::script::regex::line_char;
+
+    static locale::id id;
+
+#if !defined(_MSC_VER) || _MSC_VER >= 2000
+    explicit
+    ctype (size_t refs = 0): locale::facet (refs) {}
+#else
+    explicit
+    ctype (size_t refs = 0): ctype_base (refs) {}
+#endif
+
+    // While unnecessary, let's keep for completeness.
+    //
+    virtual
+    ~ctype () override = default;
+
+    // The C++ standard requires the following functions to call their virtual
+    // (protected) do_*() counterparts that provide the real implementations.
+    // The only purpose for this indirection is to provide a user with the
+    // ability to customize existing (standard) ctype facets. As we do not
+    // provide such an ability, for simplicity we will omit the do_*()
+    // functions and provide the implementations directly. This should be safe
+    // as nobody except us could call those protected functions.
+    //
+    bool
+    is (mask m, char_type c) const
+    {
+      return m ==
+        (c.type () == line_type::special && c.special () >= 0 &&
+         build2::digit (static_cast<char> (c.special ()))
+         ? digit
+         : 0);
+    }
+
+    const char_type*
+    is (const char_type*, const char_type*, mask*) const;
+
+    const char_type*
+    scan_is (mask, const char_type*, const char_type*) const;
+
+    const char_type*
+    scan_not (mask, const char_type*, const char_type*) const;
+
+    char_type
+    toupper (char_type c) const {return c;}
+
+    const char_type*
+    toupper (char_type*, const char_type* e) const {return e;}
+
+    char_type
+    tolower (char_type c) const {return c;}
+
+    const char_type*
+    tolower (char_type*, const char_type* e) const {return e;}
+
+    char_type
+    widen (char c) const {return char_type (c);}
+
+    const char*
+    widen (const char*, const char*, char_type*) const;
+
+    char
+    narrow (char_type c, char def) const
+    {
+      return c.type () == line_type::special ? c.special () : def;
+    }
+
+    const char_type*
+    narrow (const char_type*, const char_type*, char, char*) const;
+  };
+
+  // Note: the current application locale must be the POSIX one. Otherwise the
+  // behavior is undefined.
+  //
+  template <>
+  class regex_traits<build2::test::script::regex::line_char>
+  {
+  public:
+    using char_type       = build2::test::script::regex::line_char;
+    using string_type     = build2::test::script::regex::line_string;
+    using locale_type     = build2::test::script::regex::line_char_locale;
+    using char_class_type = regex_traits<char>::char_class_type;
+
+    // Workaround for msvcrt bugs. For some reason it assumes such a members
+    // to be present in a regex_traits specialization.
+    //
+#if defined(_MSC_VER) && _MSC_VER < 2000
+    static const ctype_base::mask _Ch_upper = ctype_base::upper;
+    static const ctype_base::mask _Ch_alpha = ctype_base::alpha;
+
+    // Unsigned char_type. msvcrt statically asserts the _Uelem type is
+    // unsigned, so we specialize is_unsigned<line_char> as well (see below).
+    //
+    using _Uelem = char_type;
+#endif
+
+    regex_traits () = default; // Unnecessary but let's keep for completeness.
+
+    static size_t
+    length (const char_type* p) {return string_type::traits_type::length (p);}
+
+    char_type
+    translate (char_type c) const {return c;}
+
+    // Case-insensitive matching is not supported by line_regex. So there is no
+    // reason for the function to be called.
+    //
+    char_type
+    translate_nocase (char_type c) const {assert (false); return c;}
+
+    // Return a sort-key - the exact copy of [b, e).
+    //
+    template <typename I>
+    string_type
+    transform (I b, I e) const {return string_type (b, e);}
+
+    // Return a case-insensitive sort-key. Case-insensitive matching is not
+    // supported by line_regex. So there is no reason for the function to be
+    // called.
+    //
+    template <typename I>
+    string_type
+    transform_primary (I b, I e) const
+    {
+      assert (false);
+      return string_type (b, e);
+    }
+
+    // POSIX regex grammar and collating elements (e.g., [.tilde.]) in
+    // particular are not supported. So there is no reason for the function to
+    // be called.
+    //
+    template <typename I>
+    string_type
+    lookup_collatename (I, I) const {assert (false); return string_type ();}
+
+    // Character classes (e.g., [:lower:]) are not supported. So there is no
+    // reason for the function to be called.
+    //
+    template <typename I>
+    char_class_type
+    lookup_classname (I, I, bool = false) const
+    {
+      assert (false);
+      return char_class_type ();
+    }
+
+    // Return false as we don't support character classes (e.g., [:lower:]).
+    //
+    bool
+    isctype (char_type, char_class_type) const {return false;}
+
+    int
+    value (char_type, int) const;
+
+    // Return the locale passed as an argument as we do not expect anything
+    // other than POSIX locale, that we also assume to be imbued by default.
+    //
+    locale_type
+    imbue (locale_type l) {return l;}
+
+    locale_type
+    getloc () const {return locale_type ();}
+  };
+
+  // We assume line_char to be an unsigned type and express that with the
+  // following specializations used by basic_regex implementations.
+  //
+  // libstdc++ defines unsigned CharT type (regex_traits template parameter)
+  // to use as an index in some internal cache regardless if the cache is used
+  // for this specialization (and the cache is used only if CharT is char).
+  //
+  template <>
+  struct make_unsigned<build2::test::script::regex::line_char>
+  {
+    using type = build2::test::script::regex::line_char;
+  };
+
+  // msvcrt assumes regex_traits<line_char>::_Uelem to be present (see above)
+  // and statically asserts it is unsigned.
+  //
+  // And starting from VC 16.1, is_unsigned_v is not implemented in terms of
+  // is_unsigned so we have to get deeper into the implementation details.
+  //
+#if defined(_MSC_VER) && _MSC_VER >= 1921
+  template <>
+  struct _Sign_base<build2::test::script::regex::line_char, false>
+  {
+    static constexpr bool _Signed   = false;
+    static constexpr bool _Unsigned = true;
+  };
+#else
+  template <>
+  struct is_unsigned<build2::test::script::regex::line_char>
+  {
+    static const bool value = true;
+  };
+#endif
+
+  // When used with libc++ the linker complains that it can't find
+  // __match_any_but_newline<line_char>::__exec() function. The problem is
+  // that the function is only specialized for char and wchar_t
+  // (LLVM bug #31409). As line_char has no notion of the newline character we
+  // specialize the class template to behave as the __match_any<line_char>
+  // instantiation does (that luckily has all the functions in place).
+  //
+#if defined(_LIBCPP_VERSION) && _LIBCPP_VERSION <= 8000
+  template <>
+  class __match_any_but_newline<build2::test::script::regex::line_char>
+    : public __match_any<build2::test::script::regex::line_char>
+  {
+  public:
+    using base = __match_any<build2::test::script::regex::line_char>;
+    using base::base;
+  };
+#endif
+}
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      namespace regex
+      {
+        class line_regex: public std::basic_regex<line_char>
+        {
+        public:
+          using base_type = std::basic_regex<line_char>;
+
+          using base_type::base_type;
+
+          line_regex () = default;
+
+          // Move string regex together with the pool used to create it.
+          //
+          line_regex (line_string&& s, line_pool&& p)
+              // No move-string ctor for base_type, so emulate it.
+              //
+              : base_type (s), pool (move (p)) {s.clear ();}
+
+          // Move constuctible/assignable-only type.
+          //
+          line_regex (line_regex&&) = default;
+          line_regex (const line_regex&) = delete;
+          line_regex& operator= (line_regex&&) = default;
+          line_regex& operator= (const line_regex&) = delete;
+
+        public:
+          line_pool pool;
+        };
+      }
+    }
+  }
+}
+
+#include <libbuild2/test/script/regex.ixx>
+
+#endif // LIBBUILD2_TEST_SCRIPT_REGEX_HXX
diff --git a/libbuild2/test/script/regex.ixx b/libbuild2/test/script/regex.ixx
new file mode 100644
index 0000000..c5b638e
--- /dev/null
+++ b/libbuild2/test/script/regex.ixx
@@ -0,0 +1,35 @@
+// file      : libbuild2/test/script/regex.ixx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      namespace regex
+      {
+        inline char_flags
+        operator&= (char_flags& x, char_flags y)
+        {
+          return x = static_cast<char_flags> (
+            static_cast<uint16_t> (x) & static_cast<uint16_t> (y));
+        }
+
+        inline char_flags
+        operator|= (char_flags& x, char_flags y)
+        {
+          return x = static_cast<char_flags> (
+            static_cast<uint16_t> (x) | static_cast<uint16_t> (y));
+        }
+
+        inline char_flags
+        operator& (char_flags x, char_flags y) {return x &= y;}
+
+        inline char_flags
+        operator| (char_flags x, char_flags y) {return x |= y;}
+      }
+    }
+  }
+}
diff --git a/libbuild2/test/script/regex.test.cxx b/libbuild2/test/script/regex.test.cxx
new file mode 100644
index 0000000..f205154
--- /dev/null
+++ b/libbuild2/test/script/regex.test.cxx
@@ -0,0 +1,302 @@
+// file      : libbuild2/test/script/regex.test.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <regex>
+#include <type_traits> // is_pod, is_array
+
+#include <libbuild2/test/script/regex.hxx>
+
+using namespace std;
+using namespace build2::test::script::regex;
+
+int
+main ()
+{
+  using lc = line_char;
+  using ls = line_string;
+  using lr = line_regex;
+  using cf = char_flags;
+  using cr = char_regex;
+
+  init (); // Initializes the testscript regex global state.
+
+  // Test line_char.
+  //
+  {
+    static_assert (is_pod<lc>::value && !is_array<lc>::value,
+                   "line_char must be char-like");
+
+    // Zero-initialed line_char should be the null-char as required by
+    // char_traits<>::length() specification.
+    //
+    assert (lc () == lc::nul);
+
+    line_pool p;
+
+    assert (lc::eof == -1);
+    assert (lc::nul == 0);
+
+    enum meta {mn = 'n', mp = 'p'};
+
+    // Special roundtrip.
+    //
+    assert (lc ('0').special ()       == '0');
+    assert (lc (0).special ()         == 0);
+    assert (lc (-1).special ()        == -1);
+    assert (lc ('p').special ()       == 'p');
+    assert (lc (u'\u2028').special () == u'\u2028');
+
+    // Special comparison.
+    //
+    assert (lc ('0') == lc ('0'));
+    assert (lc ('0') == '0');
+    assert (lc ('n') == mn);
+    assert (mn       == static_cast<meta> (lc ('n')));
+
+    assert (lc ('0') != lc ('1'));
+    assert (lc ('0') != '1');
+    assert (lc ('n') != mp);
+    assert (lc ('0') != lc ("0", p));
+    assert (lc ('0') != lc (cr ("0"), p));
+
+    assert (lc ('0') < lc ('1'));
+    assert (lc ('0') < '1');
+    assert (lc ('1') < lc ("0", p));
+    assert (lc ('n') < mp);
+
+    assert (lc ('0') <= '1');
+    assert (lc ('0') <= lc ('1'));
+    assert (lc ('n') <= mn);
+    assert (lc ('1') <= lc ("0", p));
+
+    // Literal roundtrip.
+    //
+    assert (*lc ("abc", p).literal () == "abc");
+
+    // Literal comparison.
+    //
+    assert (lc ("a", p)            == lc ("a", p));
+    assert (lc ("a", p).literal () == lc ("a", p).literal ());
+    assert (char (lc ("a", p))     == '\a');
+
+    assert (lc ("a", p)   != lc ("b", p));
+    assert (!(lc ("a", p) != lc (cr ("a"), p)));
+    assert (lc ("a", p)   != lc (cr ("b"), p));
+
+    assert (lc ("a", p)   < lc ("b", p));
+    assert (!(lc ("a", p) < lc (cr ("a"), p)));
+
+    assert (lc ("a", p) <= lc ("b", p));
+    assert (lc ("a", p) <= lc (cr ("a"), p));
+    assert (lc ("a", p) <  lc (cr ("c"), p));
+
+    // Regex roundtrip.
+    //
+    assert (regex_match ("abc", *lc (cr ("abc"), p).regex ()));
+
+    // Regex flags.
+    //
+    // icase
+    //
+    assert (regex_match ("ABC", cr ("abc", cf::icase)));
+
+    // idot
+    //
+    assert (!regex_match ("a", cr ("[.]",  cf::idot)));
+    assert (!regex_match ("a", cr ("[\\.]", cf::idot)));
+
+    assert (regex_match  ("a", cr (".")));
+    assert (!regex_match ("a", cr (".", cf::idot)));
+    assert (regex_match  ("a", cr ("\\.", cf::idot)));
+    assert (!regex_match ("a", cr ("\\.")));
+
+    // regex::transform()
+    //
+    // The function is static and we can't test it directly. So we will test
+    // it indirectly via regex matches.
+    //
+    // @@ Would be nice to somehow address the inability to test internals (not
+    //    exposed via headers). As a part of utility library support?
+    //
+    assert (regex_match  (".a[.", cr (".\\.\\[[.]",   cf::idot)));
+    assert (regex_match  (".a[.", cr (".\\.\\[[\\.]", cf::idot)));
+    assert (!regex_match ("ba[.", cr (".\\.\\[[.]",   cf::idot)));
+    assert (!regex_match (".a[b", cr (".\\.\\[[.]",   cf::idot)));
+    assert (!regex_match (".a[b", cr (".\\.\\[[\\.]", cf::idot)));
+
+    // Regex comparison.
+    //
+    assert (lc ("a", p)        == lc (cr ("a|b"), p));
+    assert (lc (cr ("a|b"), p) == lc ("a", p));
+  }
+
+  // Test char_traits<line_char>.
+  //
+  {
+    using ct = char_traits<lc>;
+    using vc = vector<lc>;
+
+    lc c;
+    ct::assign (c, '0');
+    assert (c == ct::char_type ('0'));
+
+    assert (ct::to_char_type (c) == c);
+    assert (ct::to_int_type (c) == c);
+
+    assert (ct::eq_int_type (c, c));
+    assert (!ct::eq_int_type (c, lc::eof));
+
+    assert (ct::eof () == lc::eof);
+
+    assert (ct::not_eof (c) == c);
+    assert (ct::not_eof (lc::eof) != lc::eof);
+
+    ct::assign (&c, 1, '1');
+    assert (c == ct::int_type ('1'));
+
+    assert (ct::eq (lc ('0'), lc ('0')));
+    assert (ct::lt (lc ('0'), lc ('1')));
+
+    vc v1 ({'0', '1', '2'});
+    vc v2 (3, lc::nul);
+
+    assert (ct::find (v1.data (), 3, '1') == v1.data () + 1);
+
+    ct::copy (v2.data (), v1.data (), 3);
+    assert (v2 == v1);
+
+    v2.push_back (lc::nul);
+    assert (ct::length (v2.data ()) == 3);
+
+    // Overlaping ranges.
+    //
+    ct::move (v1.data () + 1, v1.data (), 2);
+    assert (v1 == vc ({'0', '0', '1'}));
+
+    v1 = vc ({'0', '1', '2'});
+    ct::move (v1.data (), v1.data () + 1, 2);
+    assert (v1 == vc ({'1', '2', '2'}));
+  }
+
+  // Test line_char_locale and ctype<line_char> (only non-trivial functions).
+  //
+  {
+    using ct = ctype<lc>;
+
+    line_char_locale l;
+
+    // It is better not to create q facet on stack as it is
+    // reference-countable.
+    //
+    const ct& t (use_facet<ct> (l));
+    line_pool p;
+
+    assert (t.is  (ct::digit, '0'));
+    assert (!t.is (ct::digit, '?'));
+    assert (!t.is (ct::digit, lc ("0", p)));
+
+    const lc chars[] = { '0', '?' };
+    ct::mask m[2];
+
+    const lc* b (chars);
+    const lc* e (chars + 2);
+
+    // Cast flag value to mask type and compare to mask.
+    //
+    auto fl = [] (ct::mask m, ct::mask f) {return m == f;};
+
+    t.is (b, e, m);
+    assert (fl (m[0], ct::digit) && fl (m[1], 0));
+
+    assert (t.scan_is (ct::digit, b, e) == b);
+    assert (t.scan_is (0, b, e) == b + 1);
+
+    assert (t.scan_not (ct::digit, b, e) == b + 1);
+    assert (t.scan_not (0, b, e) == b);
+
+    {
+      char nr[] = "0?";
+      lc wd[2];
+      t.widen (nr, nr + 2, wd);
+      assert (wd[0] == b[0] && wd[1] == b[1]);
+    }
+
+    {
+      lc wd[] = {'0', lc ("a", p)};
+      char nr[2];
+      t.narrow (wd, wd + 2, '-', nr);
+      assert (nr[0] == '0' && nr[1] == '-');
+    }
+  }
+
+  // Test regex_traits<line_char>. Functions other that value() are trivial.
+  //
+  {
+    regex_traits<lc> t;
+
+    const int  radix[] = {8, 10}; // Radix 16 is not supported by line_char.
+    const char digits[] = "0123456789ABCDEF";
+
+    for (size_t r (0); r < 2; ++r)
+    {
+      for (int i (0); i < radix[r]; ++i)
+        assert (t.value (digits[i], radix[r]) == i);
+    }
+  }
+
+  // Test line_regex construction.
+  //
+  {
+    line_pool p;
+    lr r1 ({lc ("foo", p), lc (cr ("ba(r|z)"), p)}, move (p));
+
+    lr r2 (move (r1));
+    assert (regex_match (ls ({lc ("foo", r2.pool), lc ("bar", r2.pool)}), r2));
+    assert (!regex_match (ls ({lc ("foo", r2.pool), lc ("ba", r2.pool)}), r2));
+  }
+
+  // Test line_regex match.
+  //
+  {
+    line_pool p;
+
+    const lc foo ("foo", p);
+    const lc bar ("bar", p);
+    const lc baz ("baz", p);
+    const lc blank ("", p);
+
+    assert (regex_match  (ls ({foo, bar}), lr ({foo, bar})));
+    assert (!regex_match (ls ({foo, baz}), lr ({foo, bar})));
+
+    assert (regex_match (ls ({bar, foo}),
+                         lr ({'(', foo, '|', bar, ')', '+'})));
+
+    assert (regex_match (ls ({foo, foo, bar}),
+                         lr ({'(', foo, ')', '\\', '1', bar})));
+
+    assert (regex_match (ls ({foo}),   lr ({lc (cr ("fo+"), p)})));
+    assert (regex_match (ls ({foo}),   lr ({lc (cr (".*"), p)})));
+    assert (regex_match (ls ({blank}), lr ({lc (cr (".*"), p)})));
+
+    assert (regex_match (ls ({blank, blank, foo}),
+                         lr ({blank, '*', foo, blank, '*'})));
+
+    assert (regex_match (ls ({blank, blank, foo}), lr ({'.', '*'})));
+
+    assert (regex_match (ls ({blank, blank}),
+                         lr ({blank, '*', foo, '?', blank, '*'})));
+
+    assert (regex_match  (ls ({foo}),      lr ({foo, '{', '1', '}'})));
+    assert (regex_match  (ls ({foo, foo}), lr ({foo, '{', '1', ',', '}'})));
+
+    assert (regex_match  (ls ({foo, foo}),
+                          lr ({foo, '{', '1', ',', '2', '}'})));
+
+    assert (!regex_match (ls ({foo, foo}),
+                          lr ({foo, '{', '3', ',', '4', '}'})));
+
+    assert (regex_match  (ls ({foo}), lr ({'(', '?', '=', foo, ')', foo})));
+    assert (regex_match  (ls ({foo}), lr ({'(', '?', '!', bar, ')', foo})));
+  }
+}
diff --git a/libbuild2/test/script/runner.cxx b/libbuild2/test/script/runner.cxx
new file mode 100644
index 0000000..6c1becd
--- /dev/null
+++ b/libbuild2/test/script/runner.cxx
@@ -0,0 +1,1891 @@
+// file      : libbuild2/test/script/runner.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/test/script/runner.hxx>
+
+#include <set>
+#include <ios> // streamsize
+
+#include <libbutl/regex.mxx>
+#include <libbutl/fdstream.mxx> // fdopen_mode, fdnull(), fddup()
+
+#include <libbuild2/variable.hxx>
+#include <libbuild2/filesystem.hxx>
+#include <libbuild2/diagnostics.hxx>
+
+#include <libbuild2/test/common.hxx>
+
+#include <libbuild2/test/script/regex.hxx>
+#include <libbuild2/test/script/parser.hxx>
+#include <libbuild2/test/script/builtin.hxx>
+
+using namespace std;
+using namespace butl;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      // Normalize a path. Also make the relative path absolute using the
+      // scope's working directory unless it is already absolute.
+      //
+      static path
+      normalize (path p, const scope& sp, const location& l)
+      {
+        path r (p.absolute () ? move (p) : sp.wd_path / move (p));
+
+        try
+        {
+          r.normalize ();
+        }
+        catch (const invalid_path& e)
+        {
+          fail (l) << "invalid file path " << e.path;
+        }
+
+        return r;
+      }
+
+      // Check if a path is not empty, the referenced file exists and is not
+      // empty.
+      //
+      static bool
+      non_empty (const path& p, const location& ll)
+      {
+        if (p.empty () || !exists (p))
+          return false;
+
+        try
+        {
+          ifdstream is (p);
+          return is.peek () != ifdstream::traits_type::eof ();
+        }
+        catch (const io_error& e)
+        {
+          // While there can be no fault of the test command being currently
+          // executed let's add the location anyway to ease the
+          // troubleshooting. And let's stick to that principle down the road.
+          //
+          fail (ll) << "unable to read " << p << ": " << e << endf;
+        }
+      }
+
+      // If the file exists, not empty and not larger than 4KB print it to the
+      // diag record. The file content goes from the new line and is not
+      // indented.
+      //
+      static void
+      print_file (diag_record& d, const path& p, const location& ll)
+      {
+        if (exists (p))
+        {
+          try
+          {
+            ifdstream is (p, ifdstream::in, ifdstream::badbit);
+
+            if (is.peek () != ifdstream::traits_type::eof ())
+            {
+              char buf[4096 + 1]; // Extra byte is for terminating '\0'.
+
+              // Note that the string is always '\0'-terminated with a maximum
+              // sizeof (buf) - 1 bytes read.
+              //
+              is.getline (buf, sizeof (buf), '\0');
+
+              // Print if the file fits 4KB-size buffer. Note that if it
+              // doesn't the failbit is set.
+              //
+              if (is.eof ())
+              {
+                // Suppress the trailing newline character as the diag record
+                // adds it's own one when flush.
+                //
+                streamsize n (is.gcount ());
+                assert (n > 0);
+
+                // Note that if the file contains '\0' it will also be counted
+                // by gcount(). But even in the worst case we will stay in the
+                // buffer boundaries (and so not crash).
+                //
+                if (buf[n - 1] == '\n')
+                  buf[n - 1] = '\0';
+
+                d << '\n' << buf;
+              }
+            }
+          }
+          catch (const io_error& e)
+          {
+            fail (ll) << "unable to read " << p << ": " << e;
+          }
+        }
+      }
+
+      // Print first 10 directory sub-entries to the diag record. The directory
+      // must exist.
+      //
+      static void
+      print_dir (diag_record& d, const dir_path& p, const location& ll)
+      {
+        try
+        {
+          size_t n (0);
+          for (const dir_entry& de: dir_iterator (p,
+                                                  false /* ignore_dangling */))
+          {
+            if (n++ < 10)
+              d << '\n' << (de.ltype () == entry_type::directory
+                            ? path_cast<dir_path> (de.path ())
+                            : de.path ());
+          }
+
+          if (n > 10)
+            d << "\nand " << n - 10 << " more file(s)";
+        }
+        catch (const system_error& e)
+        {
+          fail (ll) << "unable to iterate over " << p << ": " << e;
+        }
+      }
+
+      // Save a string to the file. Fail if exception is thrown by underlying
+      // operations.
+      //
+      static void
+      save (const path& p, const string& s, const location& ll)
+      {
+        try
+        {
+          ofdstream os (p);
+          os << s;
+          os.close ();
+        }
+        catch (const io_error& e)
+        {
+          fail (ll) << "unable to write " << p << ": " << e;
+        }
+      }
+
+      // Return the value of the test.target variable.
+      //
+      static inline const target_triplet&
+      test_target (const script& s)
+      {
+        // @@ Would be nice to use cached value from test::common_data.
+        //
+        if (auto r = cast_null<target_triplet> (s.test_target["test.target"]))
+          return *r;
+
+        // We set it to default value in init() so it can only be NULL if the
+        // user resets it.
+        //
+        fail << "invalid test.target value" << endf;
+      }
+
+      // Transform string according to here-* redirect modifiers from the {/}
+      // set.
+      //
+      static string
+      transform (const string& s,
+                 bool regex,
+                 const string& modifiers,
+                 const script& scr)
+      {
+        if (modifiers.find ('/') == string::npos)
+          return s;
+
+        // For targets other than Windows leave the string intact.
+        //
+        if (test_target (scr).class_ != "windows")
+          return s;
+
+        // Convert forward slashes to Windows path separators (escape for
+        // regex).
+        //
+        string r;
+        for (size_t p (0);;)
+        {
+          size_t sp (s.find ('/', p));
+
+          if (sp != string::npos)
+          {
+            r.append (s, p, sp - p);
+            r.append (regex ? "\\\\" : "\\");
+            p = sp + 1;
+          }
+          else
+          {
+            r.append (s, p, sp);
+            break;
+          }
+        }
+
+        return r;
+      }
+
+      // Check if the test command output matches the expected result (redirect
+      // value). Noop for redirect types other than none, here_*.
+      //
+      static bool
+      check_output (const path& pr,
+                    const path& op,
+                    const path& ip,
+                    const redirect& rd,
+                    const location& ll,
+                    scope& sp,
+                    bool diag,
+                    const char* what)
+      {
+        auto input_info = [&ip, &ll] (diag_record& d)
+        {
+          if (non_empty (ip, ll))
+            d << info << "stdin: " << ip;
+        };
+
+        auto output_info = [&what, &ll] (diag_record& d,
+                                         const path& p,
+                                         const char* prefix = "",
+                                         const char* suffix = "")
+        {
+          if (non_empty (p, ll))
+            d << info << prefix << what << suffix << ": " << p;
+          else
+            d << info << prefix << what << suffix << " is empty";
+        };
+
+        if (rd.type == redirect_type::none)
+        {
+          // Check that there is no output produced.
+          //
+          assert (!op.empty ());
+
+          if (!non_empty (op, ll))
+            return true;
+
+          if (diag)
+          {
+            diag_record d (error (ll));
+            d << pr << " unexpectedly writes to " << what <<
+              info << what << ": " << op;
+
+            input_info (d);
+
+            // Print cached output.
+            //
+            print_file (d, op, ll);
+          }
+
+          // Fall through (to return false).
+          //
+        }
+        else if (rd.type == redirect_type::here_str_literal ||
+                 rd.type == redirect_type::here_doc_literal ||
+                 (rd.type == redirect_type::file &&
+                  rd.file.mode == redirect_fmode::compare))
+        {
+          // The expected output is provided as a file or as a string. Save the
+          // string to a file in the later case.
+          //
+          assert (!op.empty ());
+
+          path eop;
+
+          if (rd.type == redirect_type::file)
+            eop = normalize (rd.file.path, sp, ll);
+          else
+          {
+            eop = path (op + ".orig");
+            save (eop, transform (rd.str, false, rd.modifiers, *sp.root), ll);
+            sp.clean_special (eop);
+          }
+
+          // Use the diff utility for comparison.
+          //
+          path dp ("diff");
+          process_path pp (run_search (dp, true));
+
+          cstrings args {pp.recall_string (), "-u"};
+
+          // Ignore Windows newline fluff if that's what we are running on.
+          //
+          if (test_target (*sp.root).class_ == "windows")
+            args.push_back ("--strip-trailing-cr");
+
+          args.push_back (eop.string ().c_str ());
+          args.push_back (op.string ().c_str ());
+          args.push_back (nullptr);
+
+          if (verb >= 2)
+            print_process (args);
+
+          try
+          {
+            // Save diff's stdout to a file for troubleshooting and for the
+            // optional (if not too large) printing (at the end of
+            // diagnostics).
+            //
+            path ep (op + ".diff");
+            auto_fd efd;
+
+            try
+            {
+              efd = fdopen (ep, fdopen_mode::out | fdopen_mode::create);
+              sp.clean_special (ep);
+            }
+            catch (const io_error& e)
+            {
+              fail (ll) << "unable to write " << ep << ": " << e;
+            }
+
+            // Diff utility prints the differences to stdout. But for the
+            // user it is a part of the test failure diagnostics so let's
+            // redirect stdout to stderr.
+            //
+            process p (pp, args.data (), 0, 2, efd.get ());
+            efd.reset ();
+
+            if (p.wait ())
+              return true;
+
+            assert (p.exit);
+            const process_exit& pe (*p.exit);
+
+            // Note that both POSIX and GNU diff report error by exiting with
+            // the code > 1.
+            //
+            if (!pe.normal () || pe.code () > 1)
+            {
+              diag_record d (fail (ll));
+              print_process (d, args);
+              d << " " << pe;
+            }
+
+            // Output doesn't match the expected result.
+            //
+            if (diag)
+            {
+              diag_record d (error (ll));
+              d << pr << " " << what << " doesn't match expected";
+
+              output_info (d, op);
+              output_info (d, eop, "expected ");
+              output_info (d, ep, "", " diff");
+              input_info  (d);
+
+              print_file (d, ep, ll);
+            }
+
+            // Fall through (to return false).
+            //
+          }
+          catch (const process_error& e)
+          {
+            error (ll) << "unable to execute " << pp << ": " << e;
+
+            if (e.child)
+              exit (1);
+
+            throw failed ();
+          }
+        }
+        else if (rd.type == redirect_type::here_str_regex ||
+                 rd.type == redirect_type::here_doc_regex)
+        {
+          // The overall plan is:
+          //
+          // 1. Create regex line string. While creating it's line characters
+          //    transform regex lines according to the redirect modifiers.
+          //
+          // 2. Create line regex using the line string. If creation fails
+          //    then save the (transformed) regex redirect to a file for
+          //    troubleshooting.
+          //
+          // 3. Parse the output into the literal line string.
+          //
+          // 4. Match the output line string with the line regex.
+          //
+          // 5. If match fails save the (transformed) regex redirect to a file
+          //    for troubleshooting.
+          //
+          using namespace regex;
+
+          assert (!op.empty ());
+
+          // Create regex line string.
+          //
+          line_pool pool;
+          line_string rls;
+          const regex_lines rl (rd.regex);
+
+          // Parse regex flags.
+          //
+          // When add support for new flags don't forget to update
+          // parse_regex().
+          //
+          auto parse_flags = [] (const string& f) -> char_flags
+          {
+            char_flags r (char_flags::none);
+
+            for (char c: f)
+            {
+              switch (c)
+              {
+              case 'd': r |= char_flags::idot;  break;
+              case 'i': r |= char_flags::icase; break;
+              default: assert (false); // Error so should have been checked.
+              }
+            }
+
+            return r;
+          };
+
+          // Return original regex line with the transformation applied.
+          //
+          auto line = [&rl, &rd, &sp] (const regex_line& l) -> string
+          {
+            string r;
+            if (l.regex)                  // Regex (possibly empty),
+            {
+              r += rl.intro;
+              r += transform (l.value, true, rd.modifiers, *sp.root);
+              r += rl.intro;
+              r += l.flags;
+            }
+            else if (!l.special.empty ()) // Special literal.
+              r += rl.intro;
+            else                          // Textual literal.
+              r += transform (l.value, false, rd.modifiers, *sp.root);
+
+            r += l.special;
+            return r;
+          };
+
+          // Return regex line location.
+          //
+          // Note that we rely on the fact that the command and regex lines
+          // are always belong to the same testscript file.
+          //
+          auto loc = [&ll] (uint64_t line, uint64_t column) -> location
+          {
+            location r (ll);
+            r.line = line;
+            r.column = column;
+            return r;
+          };
+
+          // Save the regex to file for troubleshooting, return the file path
+          // it have been saved to.
+          //
+          // Note that we save the regex on line regex creation failure or if
+          // the program output doesn't match.
+          //
+          auto save_regex = [&op, &rl, &rd, &ll, &line] () -> path
+          {
+            path rp (op + ".regex");
+
+            // Encode here-document regex global flags if present as a file
+            // name suffix. For example if icase and idot flags are specified
+            // the name will look like:
+            //
+            // test/1/stdout.regex-di
+            //
+            if (rd.type == redirect_type::here_doc_regex && !rl.flags.empty ())
+              rp += '-' + rl.flags;
+
+            // Note that if would be more efficient to directly write chunks
+            // to file rather than to compose a string first. Hower we don't
+            // bother (about performance) for the sake of the code as we
+            // already failed.
+            //
+            string s;
+            for (auto b (rl.lines.cbegin ()), i (b), e (rl.lines.cend ());
+                 i != e; ++i)
+            {
+              if (i != b) s += '\n';
+              s += line (*i);
+            }
+
+            save (rp, s, ll);
+            return rp;
+          };
+
+          // Finally create regex line string.
+          //
+          // Note that diagnostics doesn't refer to the program path as it is
+          // irrelevant to failures at this stage.
+          //
+          char_flags gf (parse_flags (rl.flags)); // Regex global flags.
+
+          for (const auto& l: rl.lines)
+          {
+            if (l.regex) // Regex (with optional special characters).
+            {
+              line_char c;
+
+              // Empty regex is a special case repesenting the blank line.
+              //
+              if (l.value.empty ())
+                c = line_char ("", pool);
+              else
+              {
+                try
+                {
+                  string s (transform (l.value, true, rd.modifiers, *sp.root));
+
+                  c = line_char (
+                    char_regex (s, gf | parse_flags (l.flags)), pool);
+                }
+                catch (const regex_error& e)
+                {
+                  // Print regex_error description if meaningful.
+                  //
+                  diag_record d (fail (loc (l.line, l.column)));
+
+                  if (rd.type == redirect_type::here_str_regex)
+                    d << "invalid " << what << " regex redirect" << e <<
+                      info << "regex: '" << line (l) << "'";
+                  else
+                    d << "invalid char-regex in " << what << " regex redirect"
+                      << e <<
+                      info << "regex line: '" << line (l) << "'";
+
+                  d << endf;
+                }
+              }
+
+              rls += c; // Append blank literal or regex line char.
+            }
+            else if (!l.special.empty ()) // Special literal.
+            {
+              // Literal can not be followed by special characters in the same
+              // line.
+              //
+              assert (l.value.empty ());
+            }
+            else // Textual literal.
+            {
+              // Append literal line char.
+              //
+              rls += line_char (
+                transform (l.value, false, rd.modifiers, *sp.root), pool);
+            }
+
+            for (char c: l.special)
+            {
+              if (line_char::syntax (c))
+                rls += line_char (c); // Append special line char.
+              else
+                fail (loc (l.line, l.column))
+                  << "invalid syntax character '" << c << "' in " << what
+                  << " regex redirect" <<
+                  info << "regex line: '" << line (l) << "'";
+            }
+          }
+
+          // Create line regex.
+          //
+          line_regex regex;
+
+          try
+          {
+            regex = line_regex (move (rls), move (pool));
+          }
+          catch (const regex_error& e)
+          {
+            // Note that line regex creation can not fail for here-string
+            // redirect as it doesn't have syntax line chars. That in
+            // particular means that end_line and end_column are meaningful.
+            //
+            assert (rd.type == redirect_type::here_doc_regex);
+
+            diag_record d (fail (loc (rd.end_line, rd.end_column)));
+
+            // Print regex_error description if meaningful.
+            //
+            d << "invalid " << what << " regex redirect" << e;
+
+            output_info (d, save_regex (), "", " regex");
+          }
+
+          // Parse the output into the literal line string.
+          //
+          line_string ls;
+
+          try
+          {
+            // Do not throw when eofbit is set (end of stream reached), and
+            // when failbit is set (getline() failed to extract any character).
+            //
+            // Note that newlines are treated as line-chars separators. That
+            // in particular means that the trailing newline produces a blank
+            // line-char (empty literal). Empty output produces the zero-length
+            // line-string.
+            //
+            // Also note that we strip the trailing CR characters (otherwise
+            // can mismatch when cross-test).
+            //
+            ifdstream is (op, ifdstream::in, ifdstream::badbit);
+            is.peek (); // Sets eofbit for an empty stream.
+
+            while (!is.eof ())
+            {
+              string s;
+              getline (is, s);
+
+              // It is safer to strip CRs in cycle, as msvcrt unexplainably
+              // adds too much trailing junk to the system_error descriptions,
+              // and so it can appear in programs output. For example:
+              //
+              // ...: Invalid data.\r\r\n
+              //
+              // Note that our custom operator<<(ostream&, const exception&)
+              // removes this junk.
+              //
+              while (!s.empty () && s.back () == '\r')
+                s.pop_back ();
+
+              ls += line_char (move (s), regex.pool);
+            }
+          }
+          catch (const io_error& e)
+          {
+            fail (ll) << "unable to read " << op << ": " << e;
+          }
+
+          // Match the output with the regex.
+          //
+          if (regex_match (ls, regex)) // Doesn't throw.
+            return true;
+
+          // Output doesn't match the regex. We save the regex to file for
+          // troubleshooting regardless of whether we print the diagnostics or
+          // not.
+          //
+          path rp (save_regex ());
+
+          if (diag)
+          {
+            diag_record d (error (ll));
+            d << pr << " " << what << " doesn't match regex";
+
+            output_info (d, op);
+            output_info (d, rp, "", " regex");
+            input_info  (d);
+
+            // Print cached output.
+            //
+            print_file (d, op, ll);
+          }
+
+          // Fall through (to return false).
+          //
+        }
+        else // Noop.
+          return true;
+
+        return false;
+      }
+
+      bool default_runner::
+      test (scope& s) const
+      {
+        return common_.test (s.root->test_target, s.id_path);
+      }
+
+      void default_runner::
+      enter (scope& sp, const location&)
+      {
+        auto df = make_diag_frame (
+          [&sp](const diag_record& dr)
+          {
+            // Let's not depend on how the path representation can be improved
+            // for readability on printing.
+            //
+            dr << info << "test id: " << sp.id_path.posix_string ();
+          });
+
+        // Scope working directory shall be empty (the script working
+        // directory is cleaned up by the test rule prior the script
+        // execution).
+        //
+        // Create the root working directory containing the .buildignore file
+        // to make sure that it is ignored by name patterns (see buildignore
+        // description for details).
+        //
+        // @@ Shouldn't we add an optional location parameter to mkdir() and
+        // alike utility functions so the failure message can contain
+        // location info?
+        //
+        fs_status<mkdir_status> r (
+          sp.parent == nullptr
+          ? mkdir_buildignore (
+            sp.wd_path,
+            sp.root->target_scope.root_scope ()->root_extra->buildignore_file,
+            2)
+          : mkdir (sp.wd_path, 2));
+
+        if (r == mkdir_status::already_exists)
+          fail << "working directory " << sp.wd_path << " already exists" <<
+            info << "are tests stomping on each other's feet?";
+
+        // We don't change the current directory here but indicate that the
+        // scope test commands will be executed in that directory.
+        //
+        if (verb >= 2)
+          text << "cd " << sp.wd_path;
+
+        sp.clean ({cleanup_type::always, sp.wd_path}, true);
+      }
+
+      void default_runner::
+      leave (scope& sp, const location& ll)
+      {
+        auto df = make_diag_frame (
+          [&sp](const diag_record& dr)
+          {
+            // Let's not depend on how the path representation can be improved
+            // for readability on printing.
+            //
+            dr << info << "test id: " << sp.id_path.posix_string ();
+          });
+
+        // Perform registered cleanups if requested.
+        //
+        if (common_.after == output_after::clean)
+        {
+          // Note that we operate with normalized paths here.
+          //
+          // Remove special files. The order is not important as we don't
+          // expect directories here.
+          //
+          for (const auto& p: sp.special_cleanups)
+          {
+            // Remove the file if exists. Fail otherwise.
+            //
+            if (rmfile (p, 3) == rmfile_status::not_exist)
+              fail (ll) << "registered for cleanup special file " << p
+                        << " does not exist";
+          }
+
+          // Remove files and directories in the order opposite to the order of
+          // cleanup registration.
+          //
+          for (const auto& c: reverse_iterate (sp.cleanups))
+          {
+            cleanup_type t (c.type);
+
+            // Skip whenever the path exists or not.
+            //
+            if (t == cleanup_type::never)
+              continue;
+
+            const path& cp (c.path);
+
+            // Wildcard with the last component being '***' (without trailing
+            // separator) matches all files and sub-directories recursively as
+            // well as the start directories itself. So we will recursively
+            // remove the directories that match the parent (for the original
+            // path) directory wildcard.
+            //
+            bool recursive (cp.leaf ().representation () == "***");
+            const path& p (!recursive ? cp : cp.directory ());
+
+            // Remove files or directories using wildcard.
+            //
+            if (p.string ().find_first_of ("?*") != string::npos)
+            {
+              bool removed (false);
+
+              auto rm = [&cp, recursive, &removed, &sp, &ll] (path&& pe,
+                                                              const string&,
+                                                              bool interm)
+              {
+                if (!interm)
+                {
+                  // While removing the entry we can get not_exist due to
+                  // racing conditions, but that's ok if somebody did our job.
+                  // Note that we still set the removed flag to true in this
+                  // case.
+                  //
+                  removed = true; // Will be meaningless on failure.
+
+                  if (pe.to_directory ())
+                  {
+                    dir_path d (path_cast<dir_path> (pe));
+
+                    if (!recursive)
+                    {
+                      rmdir_status r (rmdir (d, 3));
+
+                      if (r != rmdir_status::not_empty)
+                        return true;
+
+                      diag_record dr (fail (ll));
+                      dr << "registered for cleanup directory " << d
+                         << " is not empty";
+
+                      print_dir (dr, d, ll);
+                      dr << info << "wildcard: '" << cp << "'";
+                    }
+                    else
+                    {
+                      // Don't remove the working directory (it will be removed
+                      // by the dedicated cleanup).
+                      //
+                      // Cast to uint16_t to avoid ambiguity with
+                      // libbutl::rmdir_r().
+                      //
+                      rmdir_status r (rmdir_r (d,
+                                               d != sp.wd_path,
+                                               static_cast<uint16_t> (3)));
+
+                      if (r != rmdir_status::not_empty)
+                        return true;
+
+                      // The directory is unlikely to be current but let's keep
+                      // for completeness.
+                      //
+                      fail (ll) << "registered for cleanup wildcard " << cp
+                                << " matches the current directory";
+                    }
+                  }
+                  else
+                    rmfile (pe, 3);
+                }
+
+                return true;
+              };
+
+              // Note that here we rely on the fact that recursive iterating
+              // goes depth-first (which make sense for the cleanup).
+              //
+              try
+              {
+                // Doesn't follow symlinks.
+                //
+                path_search (p,
+                             rm,
+                             dir_path () /* start */,
+                             path_match_flags::none);
+              }
+              catch (const system_error& e)
+              {
+                fail (ll) << "unable to cleanup wildcard " << cp << ": " << e;
+              }
+
+              // Removal of no filesystem entries is not an error for 'maybe'
+              // cleanup type.
+              //
+              if (removed || t == cleanup_type::maybe)
+                continue;
+
+              fail (ll) << "registered for cleanup wildcard " << cp
+                        << " doesn't match any "
+                        << (recursive
+                            ? "path"
+                            : p.to_directory ()
+                              ? "directory"
+                              : "file");
+            }
+
+            // Remove the directory if exists and empty. Fail otherwise.
+            // Removal of non-existing directory is not an error for 'maybe'
+            // cleanup type.
+            //
+            if (p.to_directory ())
+            {
+              dir_path d (path_cast<dir_path> (p));
+              bool wd (d == sp.wd_path);
+
+              // Trace the scope working directory removal with the verbosity
+              // level 2 (that was used for its creation). For other
+              // directories use level 3 (as for other cleanups).
+              //
+              int v (wd ? 2 : 3);
+
+              // Don't remove the working directory for the recursive cleanup
+              // (it will be removed by the dedicated one).
+              //
+              // Note that the root working directory contains the
+              // .buildignore file (see above).
+              //
+              // @@ If 'd' is a file then will fail with a diagnostics having
+              //    no location info. Probably need to add an optional location
+              //    parameter to rmdir() function. The same problem exists for
+              //    a file cleanup when try to rmfile() directory instead of
+              //    file.
+              //
+              rmdir_status r (
+                recursive
+                ? rmdir_r (d, !wd, static_cast <uint16_t> (v))
+                : (wd && sp.parent == nullptr
+                   ? rmdir_buildignore (
+                       d,
+                       sp.root->target_scope.root_scope ()->root_extra->buildignore_file,
+                       v)
+                   : rmdir (d, v)));
+
+              if (r == rmdir_status::success ||
+                  (r == rmdir_status::not_exist && t == cleanup_type::maybe))
+                continue;
+
+              diag_record dr (fail (ll));
+              dr << "registered for cleanup directory " << d
+                 << (r == rmdir_status::not_exist
+                     ? " does not exist"
+                     : !recursive
+                       ? " is not empty"
+                       : " is current");
+
+              if (r == rmdir_status::not_empty)
+                print_dir (dr, d, ll);
+            }
+
+            // Remove the file if exists. Fail otherwise. Removal of
+            // non-existing file is not an error for 'maybe' cleanup type.
+            //
+            if (rmfile (p, 3) == rmfile_status::not_exist &&
+                t == cleanup_type::always)
+              fail (ll) << "registered for cleanup file " << p
+                        << " does not exist";
+          }
+        }
+
+        // Return to the parent scope directory or to the out_base one for the
+        // script scope.
+        //
+        if (verb >= 2)
+          text << "cd " << (sp.parent != nullptr
+                            ? sp.parent->wd_path
+                            : sp.wd_path.directory ());
+      }
+
+      // The exit pseudo-builtin: exit the current scope successfully, or
+      // print the diagnostics and exit the current scope and all the outer
+      // scopes unsuccessfully. Always throw exit_scope exception.
+      //
+      // exit [<diagnostics>]
+      //
+      [[noreturn]] static void
+      exit_builtin (const strings& args, const location& ll)
+      {
+        auto i (args.begin ());
+        auto e (args.end ());
+
+        // Process arguments.
+        //
+        // If no argument is specified, then exit successfully. Otherwise,
+        // print the diagnostics and exit unsuccessfully.
+        //
+        if (i == e)
+          throw exit_scope (true);
+
+        const string& s (*i++);
+
+        if (i != e)
+          fail (ll) << "unexpected argument '" << *i << "'";
+
+        error (ll) << s;
+        throw exit_scope (false);
+      }
+
+      // The set pseudo-builtin: set variable from the stdin input.
+      //
+      // set [-e|--exact] [(-n|--newline)|(-w|--whitespace)] [<attr>] <var>
+      //
+      static void
+      set_builtin (scope& sp,
+                   const strings& args,
+                   auto_fd in,
+                   const location& ll)
+      {
+        try
+        {
+          // Do not throw when eofbit is set (end of stream reached), and
+          // when failbit is set (read operation failed to extract any
+          // character).
+          //
+          ifdstream cin  (move (in), ifdstream::badbit);
+
+          auto i (args.begin ());
+          auto e (args.end ());
+
+          // Process options.
+          //
+          bool exact (false);
+          bool newline (false);
+          bool whitespace (false);
+
+          for (; i != e; ++i)
+          {
+            const string& o (*i);
+
+            if (o == "-e" || o == "--exact")
+              exact = true;
+            else if (o == "-n" || o == "--newline")
+              newline = true;
+            else if (o == "-w" || o == "--whitespace")
+              whitespace = true;
+            else
+            {
+              if (*i == "--")
+                ++i;
+
+              break;
+            }
+          }
+
+          // Process arguments.
+          //
+          if (i == e)
+            fail (ll) << "missing variable name";
+
+          const string& a (*i++); // Either attributes or variable name.
+          const string* ats (i == e ? nullptr : &a);
+          const string& vname (i == e ? a : *i++);
+
+          if (i != e)
+            fail (ll) << "unexpected argument '" << *i << "'";
+
+          if (ats != nullptr && ats->empty ())
+            fail (ll) << "empty variable attributes";
+
+          if (vname.empty ())
+            fail (ll) << "empty variable name";
+
+          // Read the input.
+          //
+          cin.peek (); // Sets eofbit for an empty stream.
+
+          names ns;
+          while (!cin.eof ())
+          {
+            // Read next element that depends on the whitespace mode being
+            // enabled or not. For the later case it also make sense to strip
+            // the trailing CRs that can appear while cross-testing Windows
+            // target or as a part of msvcrt junk production (see above).
+            //
+            string s;
+            if (whitespace)
+              cin >> s;
+            else
+            {
+              getline (cin, s);
+
+              while (!s.empty () && s.back () == '\r')
+                s.pop_back ();
+            }
+
+            // If failbit is set then we read nothing into the string as eof is
+            // reached. That in particular means that the stream has trailing
+            // whitespaces (possibly including newlines) if the whitespace mode
+            // is enabled, or the trailing newline otherwise. If so then
+            // we append the "blank" to the variable value in the exact mode
+            // prior to bailing out.
+            //
+            if (cin.fail ())
+            {
+              if (exact)
+              {
+                if (whitespace || newline)
+                  ns.emplace_back (move (s)); // Reuse empty string.
+                else if (ns.empty ())
+                  ns.emplace_back ("\n");
+                else
+                  ns[0].value += '\n';
+              }
+
+              break;
+            }
+
+            if (whitespace || newline || ns.empty ())
+              ns.emplace_back (move (s));
+            else
+            {
+              ns[0].value += '\n';
+              ns[0].value += s;
+            }
+          }
+
+          cin.close ();
+
+          // Set the variable value and attributes. Note that we need to aquire
+          // unique lock before potentially changing the script's variable
+          // pool. The obtained variable reference can safelly be used with no
+          // locking as the variable pool is an associative container
+          // (underneath) and we are only adding new variables into it.
+          //
+          ulock ul (sp.root->var_pool_mutex);
+          const variable& var (sp.root->var_pool.insert (move (vname)));
+          ul.unlock ();
+
+          value& lhs (sp.assign (var));
+
+          // If there are no attributes specified then the variable assignment
+          // is straightforward. Otherwise we will use the build2 parser helper
+          // function.
+          //
+          if (ats == nullptr)
+            lhs.assign (move (ns), &var);
+          else
+          {
+            // If there is an error in the attributes string, our diagnostics
+            // will look like this:
+            //
+            // <attributes>:1:1 error: unknown value attribute x
+            //   testscript:10:1 info: while parsing attributes '[x]'
+            //
+            auto df = make_diag_frame (
+              [ats, &ll](const diag_record& dr)
+              {
+                dr << info (ll) << "while parsing attributes '" << *ats << "'";
+              });
+
+            parser p;
+            p.apply_value_attributes (&var,
+                                      lhs,
+                                      value (move (ns)),
+                                      *ats,
+                                      token_type::assign,
+                                      path ("<attributes>"));
+          }
+        }
+        catch (const io_error& e)
+        {
+          fail (ll) << "set: " << e;
+        }
+      }
+
+      static bool
+      run_pipe (scope& sp,
+                command_pipe::const_iterator bc,
+                command_pipe::const_iterator ec,
+                auto_fd ifd,
+                size_t ci, size_t li, const location& ll,
+                bool diag)
+      {
+        if (bc == ec) // End of the pipeline.
+          return true;
+
+        // The overall plan is to run the first command in the pipe, reading
+        // its input from the file descriptor passed (or, for the first
+        // command, according to stdin redirect specification) and redirecting
+        // its output to the right-hand part of the pipe recursively. Fail if
+        // the right-hand part fails. Otherwise check the process exit code,
+        // match stderr (and stdout for the last command in the pipe) according
+        // to redirect specification(s) and fail if any of the above fails.
+        //
+        const command& c (*bc);
+
+        // Register the command explicit cleanups. Verify that the path being
+        // cleaned up is a sub-path of the testscript working directory. Fail
+        // if this is not the case.
+        //
+        for (const auto& cl: c.cleanups)
+        {
+          const path& p (cl.path);
+          path np (normalize (p, sp, ll));
+
+          const string& ls (np.leaf ().string ());
+          bool wc (ls == "*" || ls == "**" || ls == "***");
+          const path& cp (wc ? np.directory () : np);
+          const dir_path& wd (sp.root->wd_path);
+
+          if (!cp.sub (wd))
+            fail (ll) << (wc
+                          ? "wildcard"
+                          : p.to_directory ()
+                            ? "directory"
+                            : "file")
+                      << " cleanup " << p << " is out of working directory "
+                      << wd;
+
+          sp.clean ({cl.type, move (np)}, false);
+        }
+
+        const redirect& in  (c.in.effective ());
+        const redirect& out (c.out.effective ());
+        const redirect& err (c.err.effective ());
+        bool eq (c.exit.comparison == exit_comparison::eq);
+
+        // If stdin file descriptor is not open then this is the first pipeline
+        // command.
+        //
+        bool first (ifd.get () == -1);
+
+        command_pipe::const_iterator nc (bc + 1);
+        bool last (nc == ec);
+
+        // Prior to opening file descriptors for command input/output
+        // redirects let's check if the command is the exit builtin. Being a
+        // builtin syntactically it differs from the regular ones in a number
+        // of ways. It doesn't communicate with standard streams, so
+        // redirecting them is meaningless. It may appear only as a single
+        // command in a pipeline. It doesn't return any value and stops the
+        // scope execution, so checking its exit status is meaningless as
+        // well. That all means we can short-circuit here calling the builtin
+        // and bailing out right after that. Checking that the user didn't
+        // specify any redirects or exit code check sounds like a right thing
+        // to do.
+        //
+        if (c.program.string () == "exit")
+        {
+          // In case the builtin is erroneously pipelined from the other
+          // command, we will close stdin gracefully (reading out the stream
+          // content), to make sure that the command doesn't print any
+          // unwanted diagnostics about IO operation failure.
+          //
+          // Note that dtor will ignore any errors (which is what we want).
+          //
+          ifdstream is (move (ifd), fdstream_mode::skip);
+
+          if (!first || !last)
+            fail (ll) << "exit builtin must be the only pipe command";
+
+          if (in.type != redirect_type::none)
+            fail (ll) << "exit builtin stdin cannot be redirected";
+
+          if (out.type != redirect_type::none)
+            fail (ll) << "exit builtin stdout cannot be redirected";
+
+          if (err.type != redirect_type::none)
+            fail (ll) << "exit builtin stderr cannot be redirected";
+
+          // We can't make sure that there is not exit code check. Let's, at
+          // least, check that non-zero code is not expected.
+          //
+          if (eq != (c.exit.code == 0))
+            fail (ll) << "exit builtin exit code cannot be non-zero";
+
+          exit_builtin (c.arguments, ll); // Throws exit_scope exception.
+        }
+
+        // Create a unique path for a command standard stream cache file.
+        //
+        auto std_path = [&sp, &ci, &li, &ll] (const char* n) -> path
+        {
+          path p (n);
+
+          // 0 if belongs to a single-line test scope, otherwise is the
+          // command line number (start from one) in the test scope.
+          //
+          if (li > 0)
+            p += "-" + to_string (li);
+
+          // 0 if belongs to a single-command expression, otherwise is the
+          // command number (start from one) in the expression.
+          //
+          // Note that the name like stdin-N can relate to N-th command of a
+          // single-line test or to N-th single-command line of multi-line
+          // test. These cases are mutually exclusive and so are unambiguous.
+          //
+          if (ci > 0)
+            p += "-" + to_string (ci);
+
+          return normalize (move (p), sp, ll);
+        };
+
+        // If this is the first pipeline command, then open stdin descriptor
+        // according to the redirect specified.
+        //
+        path isp;
+
+        if (!first)
+          assert (in.type == redirect_type::none); // No redirect expected.
+        else
+        {
+          // Open a file for passing to the command stdin.
+          //
+          auto open_stdin = [&isp, &ifd, &ll] ()
+          {
+            assert (!isp.empty ());
+
+            try
+            {
+              ifd = fdopen (isp, fdopen_mode::in);
+            }
+            catch (const io_error& e)
+            {
+              fail (ll) << "unable to read " << isp << ": " << e;
+            }
+          };
+
+          switch (in.type)
+          {
+          case redirect_type::pass:
+            {
+              try
+              {
+                ifd = fddup (0);
+              }
+              catch (const io_error& e)
+              {
+                fail (ll) << "unable to duplicate stdin: " << e;
+              }
+
+              break;
+            }
+
+          case redirect_type::none:
+            // Somehow need to make sure that the child process doesn't read
+            // from stdin. That is tricky to do in a portable way. Here we
+            // suppose that the program which (erroneously) tries to read some
+            // data from stdin being redirected to /dev/null fails not being
+            // able to read the expected data, and so the test doesn't pass
+            // through.
+            //
+            // @@ Obviously doesn't cover the case when the process reads
+            //    whatever available.
+            // @@ Another approach could be not to redirect stdin and let the
+            //    process to hang which can be interpreted as a test failure.
+            // @@ Both ways are quite ugly. Is there some better way to do
+            //    this?
+            //
+            // Fall through.
+            //
+          case redirect_type::null:
+            {
+              try
+              {
+                ifd = fdnull ();
+              }
+              catch (const io_error& e)
+              {
+                fail (ll) << "unable to write to null device: " << e;
+              }
+
+              break;
+            }
+
+          case redirect_type::file:
+            {
+              isp = normalize (in.file.path, sp, ll);
+
+              open_stdin ();
+              break;
+            }
+
+          case redirect_type::here_str_literal:
+          case redirect_type::here_doc_literal:
+            {
+              // We could write to the command stdin directly but instead will
+              // cache the data for potential troubleshooting.
+              //
+              isp = std_path ("stdin");
+
+              save (
+                isp, transform (in.str, false, in.modifiers, *sp.root), ll);
+
+              sp.clean_special (isp);
+
+              open_stdin ();
+              break;
+            }
+
+          case redirect_type::trace:
+          case redirect_type::merge:
+          case redirect_type::here_str_regex:
+          case redirect_type::here_doc_regex:
+          case redirect_type::here_doc_ref:   assert (false); break;
+          }
+        }
+
+        assert (ifd.get () != -1);
+
+        // Prior to opening file descriptors for command outputs redirects
+        // let's check if the command is the set builtin. Being a builtin
+        // syntactically it differs from the regular ones in a number of ways.
+        // It either succeeds or terminates abnormally, so redirecting stderr
+        // is meaningless. It also never produces any output and may appear
+        // only as a terminal command in a pipeline. That means we can
+        // short-circuit here calling the builtin and returning right after
+        // that. Checking that the user didn't specify any meaningless
+        // redirects or exit code check sounds as a right thing to do.
+        //
+        if (c.program.string () == "set")
+        {
+          if (!last)
+            fail (ll) << "set builtin must be the last pipe command";
+
+          if (out.type != redirect_type::none)
+            fail (ll) << "set builtin stdout cannot be redirected";
+
+          if (err.type != redirect_type::none)
+            fail (ll) << "set builtin stderr cannot be redirected";
+
+          if (eq != (c.exit.code == 0))
+            fail (ll) << "set builtin exit code cannot be non-zero";
+
+          set_builtin (sp, c.arguments, move (ifd), ll);
+          return true;
+        }
+
+        // Open a file for command output redirect if requested explicitly
+        // (file overwrite/append redirects) or for the purpose of the output
+        // validation (none, here_*, file comparison redirects), register the
+        // file for cleanup, return the file descriptor. Interpret trace
+        // redirect according to the verbosity level (as null if below 2, as
+        // pass otherwise). Return nullfd, standard stream descriptor duplicate
+        // or null-device descriptor for merge, pass or null redirects
+        // respectively (not opening any file).
+        //
+        auto open = [&sp, &ll, &std_path] (const redirect& r,
+                                           int dfd,
+                                           path& p) -> auto_fd
+        {
+          assert (dfd == 1 || dfd == 2);
+          const char* what (dfd == 1 ? "stdout" : "stderr");
+
+          fdopen_mode m (fdopen_mode::out | fdopen_mode::create);
+
+          auto_fd fd;
+          redirect_type rt (r.type != redirect_type::trace
+                            ? r.type
+                            : verb < 2
+                              ? redirect_type::null
+                              : redirect_type::pass);
+          switch (rt)
+          {
+          case redirect_type::pass:
+            {
+              try
+              {
+                fd = fddup (dfd);
+              }
+              catch (const io_error& e)
+              {
+                fail (ll) << "unable to duplicate " << what << ": " << e;
+              }
+
+              return fd;
+            }
+
+          case redirect_type::null:
+            {
+              try
+              {
+                fd = fdnull ();
+              }
+              catch (const io_error& e)
+              {
+                fail (ll) << "unable to write to null device: " << e;
+              }
+
+              return fd;
+            }
+
+          case redirect_type::merge:
+            {
+              // Duplicate the paired file descriptor later.
+              //
+              return fd; // nullfd
+            }
+
+          case redirect_type::file:
+            {
+              // For the cmp mode the user-provided path refers a content to
+              // match against, rather than a content to be produced (as for
+              // overwrite and append modes). And so for cmp mode we redirect
+              // the process output to a temporary file.
+              //
+              p = r.file.mode == redirect_fmode::compare
+                ? std_path (what)
+                : normalize (r.file.path, sp, ll);
+
+              m |= r.file.mode == redirect_fmode::append
+                ? fdopen_mode::at_end
+                : fdopen_mode::truncate;
+
+              break;
+            }
+
+          case redirect_type::none:
+          case redirect_type::here_str_literal:
+          case redirect_type::here_doc_literal:
+          case redirect_type::here_str_regex:
+          case redirect_type::here_doc_regex:
+            {
+              p = std_path (what);
+              m |= fdopen_mode::truncate;
+              break;
+            }
+
+          case redirect_type::trace:
+          case redirect_type::here_doc_ref: assert (false); break;
+          }
+
+          try
+          {
+            fd = fdopen (p, m);
+
+            if ((m & fdopen_mode::at_end) != fdopen_mode::at_end)
+            {
+              if (rt == redirect_type::file)
+                sp.clean ({cleanup_type::always, p}, true);
+              else
+                sp.clean_special (p);
+            }
+          }
+          catch (const io_error& e)
+          {
+            fail (ll) << "unable to write " << p << ": " << e;
+          }
+
+          return fd;
+        };
+
+        path osp;
+        fdpipe ofd;
+
+        // If this is the last command in the pipeline than redirect the
+        // command process stdout to a file. Otherwise create a pipe and
+        // redirect the stdout to the write-end of the pipe. The read-end will
+        // be passed as stdin for the next command in the pipeline.
+        //
+        // @@ Shouldn't we allow the here-* and file output redirects for a
+        //    command with pipelined output? Say if such redirect is present
+        //    then the process output is redirected to a file first (as it is
+        //    when no output pipelined), and only after the process exit code
+        //    and the output are validated the next command in the pipeline is
+        //    executed taking the file as an input. This could be usefull for
+        //    test failures investigation and for tests "tightening".
+        //
+        if (last)
+          ofd.out = open (out, 1, osp);
+        else
+        {
+          assert (out.type == redirect_type::none); // No redirect expected.
+
+          try
+          {
+            ofd = fdopen_pipe ();
+          }
+          catch (const io_error& e)
+          {
+            fail (ll) << "unable to open pipe: " << e;
+          }
+        }
+
+        path esp;
+        auto_fd efd (open (err, 2, esp));
+
+        // Merge standard streams.
+        //
+        bool mo (out.type == redirect_type::merge);
+        if (mo || err.type == redirect_type::merge)
+        {
+          auto_fd& self  (mo ? ofd.out : efd);
+          auto_fd& other (mo ? efd : ofd.out);
+
+          try
+          {
+            assert (self.get () == -1 && other.get () != -1);
+            self = fddup (other.get ());
+          }
+          catch (const io_error& e)
+          {
+            fail (ll) << "unable to duplicate " << (mo ? "stderr" : "stdout")
+                      << ": " << e;
+          }
+        }
+
+        // All descriptors should be open to the date.
+        //
+        assert (ofd.out.get () != -1 && efd.get () != -1);
+
+        optional<process_exit> exit;
+        builtin_func* bf (builtins.find (c.program.string ()));
+
+        bool success;
+
+        auto process_args = [&c] () -> cstrings
+        {
+          cstrings args {c.program.string ().c_str ()};
+
+          for (const auto& a: c.arguments)
+            args.push_back (a.c_str ());
+
+          args.push_back (nullptr);
+          return args;
+        };
+
+        if (bf != nullptr)
+        {
+          // Execute the builtin.
+          //
+          if (verb >= 2)
+            print_process (process_args ());
+
+          try
+          {
+            uint8_t r; // Storage.
+            builtin b (
+              bf (sp, r, c.arguments, move (ifd), move (ofd.out), move (efd)));
+
+            success = run_pipe (sp,
+                                nc,
+                                ec,
+                                move (ofd.in),
+                                ci + 1, li, ll, diag);
+
+            exit = process_exit (b.wait ());
+          }
+          catch (const system_error& e)
+          {
+            fail (ll) << "unable to execute " << c.program << " builtin: "
+                      << e << endf;
+          }
+        }
+        else
+        {
+          // Execute the process.
+          //
+          cstrings args (process_args ());
+
+          // Resolve the relative not simple program path against the scope's
+          // working directory. The simple one will be left for the process
+          // path search machinery.
+          //
+          path p;
+
+          try
+          {
+            p = path (args[0]);
+
+            if (p.relative () && !p.simple ())
+            {
+              p = sp.wd_path / p;
+              args[0] = p.string ().c_str ();
+            }
+          }
+          catch (const invalid_path& e)
+          {
+            fail (ll) << "invalid program path " << e.path;
+          }
+
+          try
+          {
+            process_path pp (process::path_search (args[0]));
+
+            if (verb >= 2)
+              print_process (args);
+
+            process pr (
+              pp,
+              args.data (),
+              {ifd.get (), -1}, process::pipe (ofd), {-1, efd.get ()},
+              sp.wd_path.string ().c_str ());
+
+            ifd.reset ();
+            ofd.out.reset ();
+            efd.reset ();
+
+            success = run_pipe (sp,
+                                nc,
+                                ec,
+                                move (ofd.in),
+                                ci + 1, li, ll, diag);
+
+            pr.wait ();
+
+            exit = move (pr.exit);
+          }
+          catch (const process_error& e)
+          {
+            error (ll) << "unable to execute " << args[0] << ": " << e;
+
+            if (e.child)
+              std::exit (1);
+
+            throw failed ();
+          }
+        }
+
+        assert (exit);
+
+        // If the righ-hand side pipeline failed than the whole pipeline fails,
+        // and no further checks are required.
+        //
+        if (!success)
+          return false;
+
+        const path& pr (c.program);
+
+        // If there is no valid exit code available by whatever reason then we
+        // print the proper diagnostics, dump stderr (if cached and not too
+        // large) and fail the whole test. Otherwise if the exit code is not
+        // correct then we print diagnostics if requested and fail the
+        // pipeline.
+        //
+        bool valid (exit->normal ());
+
+        // On Windows the exit code can be out of the valid codes range being
+        // defined as uint16_t.
+        //
+#ifdef _WIN32
+        if (valid)
+          valid = exit->code () < 256;
+#endif
+
+        success = valid && eq == (exit->code () == c.exit.code);
+
+        if (!valid || (!success && diag))
+        {
+          // In the presense of a valid exit code we print the diagnostics and
+          // return false rather than throw.
+          //
+          diag_record d (valid ? error (ll) : fail (ll));
+
+          if (!exit->normal ())
+            d << pr << " " << *exit;
+          else
+          {
+            uint16_t ec (exit->code ()); // Make sure is printed as integer.
+
+            if (!valid)
+              d << pr << " exit code " << ec << " out of 0-255 range";
+            else if (!success)
+            {
+              if (diag)
+                d << pr << " exit code " << ec << (eq ? " != " : " == ")
+                  << static_cast<uint16_t> (c.exit.code);
+            }
+            else
+              assert (false);
+          }
+
+          if (non_empty (esp, ll))
+            d << info << "stderr: " << esp;
+
+          if (non_empty (osp, ll))
+            d << info << "stdout: " << osp;
+
+          if (non_empty (isp, ll))
+            d << info << "stdin: " << isp;
+
+          // Print cached stderr.
+          //
+          print_file (d, esp, ll);
+        }
+
+        // If exit code is correct then check if the standard outputs match the
+        // expectations. Note that stdout is only redirected to file for the
+        // last command in the pipeline.
+        //
+        if (success)
+          success =
+            (!last ||
+             check_output (pr, osp, isp, out, ll, sp, diag, "stdout")) &&
+            check_output (pr, esp, isp, err, ll, sp, diag, "stderr");
+
+        return success;
+      }
+
+      static bool
+      run_expr (scope& sp,
+                const command_expr& expr,
+                size_t li, const location& ll,
+                bool diag)
+      {
+        // Print test id once per test expression.
+        //
+        auto df = make_diag_frame (
+          [&sp](const diag_record& dr)
+          {
+            // Let's not depend on how the path representation can be improved
+            // for readability on printing.
+            //
+            dr << info << "test id: " << sp.id_path.posix_string ();
+          });
+
+        // Commands are numbered sequentially throughout the expression
+        // starting with 1. Number 0 means the command is a single one.
+        //
+        size_t ci (expr.size () == 1 && expr.back ().pipe.size () == 1
+                   ? 0
+                   : 1);
+
+        // If there is no ORs to the right of a pipe then the pipe failure is
+        // fatal for the whole expression. In particular, the pipe must print
+        // the diagnostics on failure (if generally allowed). So we find the
+        // pipe that "switches on" the diagnostics potential printing.
+        //
+        command_expr::const_iterator trailing_ands; // Undefined if diag is
+                                                    // disallowed.
+        if (diag)
+        {
+          auto i (expr.crbegin ());
+          for (; i != expr.crend () && i->op == expr_operator::log_and; ++i) ;
+          trailing_ands = i.base ();
+        }
+
+        bool r (false);
+        bool print (false);
+
+        for (auto b (expr.cbegin ()), i (b), e (expr.cend ()); i != e; ++i)
+        {
+          if (diag && i + 1 == trailing_ands)
+            print = true;
+
+          const command_pipe& p (i->pipe);
+          bool or_op (i->op == expr_operator::log_or);
+
+          // Short-circuit if the pipe result must be OR-ed with true or AND-ed
+          // with false.
+          //
+          if (!((or_op && r) || (!or_op && !r)))
+            r = run_pipe (
+              sp, p.begin (), p.end (), auto_fd (), ci, li, ll, print);
+
+          ci += p.size ();
+        }
+
+        return r;
+      }
+
+      void default_runner::
+      run (scope& sp,
+           const command_expr& expr, command_type ct,
+           size_t li,
+           const location& ll)
+      {
+        // Noop for teardown commands if keeping tests output is requested.
+        //
+        if (ct == command_type::teardown &&
+            common_.after == output_after::keep)
+          return;
+
+        if (verb >= 3)
+        {
+          char c ('\0');
+
+          switch (ct)
+          {
+          case command_type::test:     c = ' '; break;
+          case command_type::setup:    c = '+'; break;
+          case command_type::teardown: c = '-'; break;
+          }
+
+          text << ": " << c << expr;
+        }
+
+        if (!run_expr (sp, expr, li, ll, true))
+          throw failed (); // Assume diagnostics is already printed.
+      }
+
+      bool default_runner::
+      run_if (scope& sp,
+              const command_expr& expr,
+              size_t li, const location& ll)
+      {
+        if (verb >= 3)
+          text << ": ?" << expr;
+
+        return run_expr (sp, expr, li, ll, false);
+      }
+    }
+  }
+}
diff --git a/libbuild2/test/script/runner.hxx b/libbuild2/test/script/runner.hxx
new file mode 100644
index 0000000..9a3f91f
--- /dev/null
+++ b/libbuild2/test/script/runner.hxx
@@ -0,0 +1,101 @@
+// file      : libbuild2/test/script/runner.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_TEST_SCRIPT_RUNNER_HXX
+#define LIBBUILD2_TEST_SCRIPT_RUNNER_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/test/script/script.hxx>
+
+namespace build2
+{
+  namespace test
+  {
+    struct common;
+
+    namespace script
+    {
+      // An exception that can be thrown by a runner to exit the scope (for
+      // example, as a result of executing the exit builtin). The status
+      // indicates whether the scope should be considered to have succeeded
+      // or failed.
+      //
+      struct exit_scope
+      {
+        bool status;
+
+        explicit
+        exit_scope (bool s): status (s) {}
+      };
+
+      class runner
+      {
+      public:
+        // Return false if this test/group should be skipped.
+        //
+        virtual bool
+        test (scope&) const = 0;
+
+        // Location is the scope start location (for diagnostics, etc).
+        //
+        virtual void
+        enter (scope&, const location&) = 0;
+
+        // Index is the 1-base index of this command line in the command list
+        // (e.g., in a compound test). If it is 0 then it means there is only
+        // one command (e.g., a simple test). This information can be used,
+        // for example, to derive file names.
+        //
+        // Location is the start position of this command line in the
+        // testscript. It can be used in diagnostics.
+        //
+        virtual void
+        run (scope&,
+             const command_expr&, command_type,
+             size_t index,
+             const location&) = 0;
+
+        virtual bool
+        run_if (scope&, const command_expr&, size_t, const location&) = 0;
+
+        // Location is the scope end location (for diagnostics, etc).
+        //
+        virtual void
+        leave (scope&, const location&) = 0;
+      };
+
+      class default_runner: public runner
+      {
+      public:
+        explicit
+        default_runner (const common& c): common_ (c) {}
+
+        virtual bool
+        test (scope& s) const override;
+
+        virtual void
+        enter (scope&, const location&) override;
+
+        virtual void
+        run (scope&,
+             const command_expr&, command_type,
+             size_t,
+             const location&) override;
+
+        virtual bool
+        run_if (scope&, const command_expr&, size_t, const location&) override;
+
+        virtual void
+        leave (scope&, const location&) override;
+
+      private:
+        const common& common_;
+      };
+    }
+  }
+}
+
+#endif // LIBBUILD2_TEST_SCRIPT_RUNNER_HXX
diff --git a/libbuild2/test/script/script.cxx b/libbuild2/test/script/script.cxx
new file mode 100644
index 0000000..b879eb4
--- /dev/null
+++ b/libbuild2/test/script/script.cxx
@@ -0,0 +1,741 @@
+// file      : libbuild2/test/script/script.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/test/script/script.hxx>
+
+#include <sstream>
+
+#include <libbuild2/target.hxx>
+#include <libbuild2/algorithm.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      ostream&
+      operator<< (ostream& o, line_type lt)
+      {
+        const char* s (nullptr);
+
+        switch (lt)
+        {
+        case line_type::var:       s = "variable"; break;
+        case line_type::cmd:       s = "command";  break;
+        case line_type::cmd_if:    s = "'if'";     break;
+        case line_type::cmd_ifn:   s = "'if!'";    break;
+        case line_type::cmd_elif:  s = "'elif'";   break;
+        case line_type::cmd_elifn: s = "'elif!'";  break;
+        case line_type::cmd_else:  s = "'else'";   break;
+        case line_type::cmd_end:   s = "'end'";    break;
+        }
+
+        return o << s;
+      }
+
+      // Quote if empty or contains spaces or any of the special characters.
+      // Note that we use single quotes since double quotes still allow
+      // expansion.
+      //
+      // @@ What if it contains single quotes?
+      //
+      static void
+      to_stream_q (ostream& o, const string& s)
+      {
+        if (s.empty () || s.find_first_of (" |&<>=\\\"") != string::npos)
+          o << '\'' << s << '\'';
+        else
+          o << s;
+      };
+
+      void
+      to_stream (ostream& o, const command& c, command_to_stream m)
+      {
+        auto print_path = [&o] (const path& p)
+        {
+          using build2::operator<<;
+
+          ostringstream s;
+          stream_verb (s, stream_verb (o));
+          s << p;
+
+          to_stream_q (o, s.str ());
+        };
+
+        auto print_redirect =
+          [&o, print_path] (const redirect& r, const char* prefix)
+        {
+          o << ' ' << prefix;
+
+          size_t n (string::traits_type::length (prefix));
+          assert (n > 0);
+
+          char d (prefix[n - 1]); // Redirect direction.
+
+          switch (r.type)
+          {
+          case redirect_type::none:  assert (false);   break;
+          case redirect_type::pass:  o << '|';         break;
+          case redirect_type::null:  o << '-';         break;
+          case redirect_type::trace: o << '!';         break;
+          case redirect_type::merge: o << '&' << r.fd; break;
+
+          case redirect_type::here_str_literal:
+          case redirect_type::here_doc_literal:
+            {
+              bool doc (r.type == redirect_type::here_doc_literal);
+
+              // For here-document add another '>' or '<'. Note that here end
+              // marker never needs to be quoted.
+              //
+              if (doc)
+                o << d;
+
+              o << r.modifiers;
+
+              if (doc)
+                o << r.end;
+              else
+              {
+                const string& v (r.str);
+                to_stream_q (o,
+                             r.modifiers.find (':') == string::npos
+                             ? string (v, 0, v.size () - 1) // Strip newline.
+                             : v);
+              }
+
+              break;
+            }
+
+          case redirect_type::here_str_regex:
+          case redirect_type::here_doc_regex:
+            {
+              bool doc (r.type == redirect_type::here_doc_regex);
+
+              // For here-document add another '>' or '<'. Note that here end
+              // marker never needs to be quoted.
+              //
+              if (doc)
+                o << d;
+
+              o << r.modifiers;
+
+              const regex_lines& re (r.regex);
+
+              if (doc)
+                o << re.intro + r.end + re.intro + re.flags;
+              else
+              {
+                assert (!re.lines.empty ()); // Regex can't be empty.
+
+                regex_line l (re.lines[0]);
+                to_stream_q (o, re.intro + l.value + re.intro + l.flags);
+              }
+
+              break;
+            }
+
+          case redirect_type::file:
+            {
+              // For stdin or stdout-comparison redirect add '>>' or '<<' (and
+              // so make it '<<<' or '>>>'). Otherwise add '+' or '=' (and so
+              // make it '>+' or '>=').
+              //
+              if (d == '<' || r.file.mode == redirect_fmode::compare)
+                o << d << d;
+              else
+                o << (r.file.mode == redirect_fmode::append ? '+' : '=');
+
+              print_path (r.file.path);
+              break;
+            }
+
+          case redirect_type::here_doc_ref: assert (false); break;
+          }
+        };
+
+        auto print_doc = [&o] (const redirect& r)
+        {
+          o << endl;
+
+          if (r.type == redirect_type::here_doc_literal)
+            o << r.str;
+          else
+          {
+            assert (r.type == redirect_type::here_doc_regex);
+
+            const regex_lines& rl (r.regex);
+
+            for (auto b (rl.lines.cbegin ()), i (b), e (rl.lines.cend ());
+                 i != e; ++i)
+            {
+              if (i != b)
+                o << endl;
+
+              const regex_line& l (*i);
+
+              if (l.regex)                  // Regex (possibly empty),
+                o << rl.intro << l.value << rl.intro << l.flags;
+              else if (!l.special.empty ()) // Special literal.
+                o << rl.intro;
+              else                          // Textual literal.
+                o << l.value;
+
+              o << l.special;
+            }
+          }
+
+          o << (r.modifiers.find (':') == string::npos ? "" : "\n") << r.end;
+        };
+
+        if ((m & command_to_stream::header) == command_to_stream::header)
+        {
+          // Program.
+          //
+          to_stream_q (o, c.program.string ());
+
+          // Arguments.
+          //
+          for (const string& a: c.arguments)
+          {
+            o << ' ';
+            to_stream_q (o, a);
+          }
+
+          // Redirects.
+          //
+          if (c.in.effective ().type  != redirect_type::none)
+            print_redirect (c.in.effective (), "<");
+
+          if (c.out.effective ().type != redirect_type::none)
+            print_redirect (c.out.effective (),  ">");
+
+          if (c.err.effective ().type != redirect_type::none)
+            print_redirect (c.err.effective (), "2>");
+
+          for (const auto& p: c.cleanups)
+          {
+            o << " &";
+
+            if (p.type != cleanup_type::always)
+              o << (p.type == cleanup_type::maybe ? '?' : '!');
+
+            print_path (p.path);
+          }
+
+          if (c.exit.comparison != exit_comparison::eq || c.exit.code != 0)
+          {
+            switch (c.exit.comparison)
+            {
+            case exit_comparison::eq: o << " == "; break;
+            case exit_comparison::ne: o << " != "; break;
+            }
+
+            o << static_cast<uint16_t> (c.exit.code);
+          }
+        }
+
+        if ((m & command_to_stream::here_doc) == command_to_stream::here_doc)
+        {
+          // Here-documents.
+          //
+          if (c.in.type == redirect_type::here_doc_literal ||
+              c.in.type == redirect_type::here_doc_regex)
+            print_doc (c.in);
+
+          if (c.out.type == redirect_type::here_doc_literal ||
+              c.out.type == redirect_type::here_doc_regex)
+            print_doc (c.out);
+
+          if (c.err.type == redirect_type::here_doc_literal ||
+              c.err.type == redirect_type::here_doc_regex)
+            print_doc (c.err);
+        }
+      }
+
+      void
+      to_stream (ostream& o, const command_pipe& p, command_to_stream m)
+      {
+        if ((m & command_to_stream::header) == command_to_stream::header)
+        {
+          for (auto b (p.begin ()), i (b); i != p.end (); ++i)
+          {
+            if (i != b)
+              o << " | ";
+
+            to_stream (o, *i, command_to_stream::header);
+          }
+        }
+
+        if ((m & command_to_stream::here_doc) == command_to_stream::here_doc)
+        {
+          for (const command& c: p)
+            to_stream (o, c, command_to_stream::here_doc);
+        }
+      }
+
+      void
+      to_stream (ostream& o, const command_expr& e, command_to_stream m)
+      {
+        if ((m & command_to_stream::header) == command_to_stream::header)
+        {
+          for (auto b (e.begin ()), i (b); i != e.end (); ++i)
+          {
+            if (i != b)
+            {
+              switch (i->op)
+              {
+              case expr_operator::log_or:  o << " || "; break;
+              case expr_operator::log_and: o << " && "; break;
+              }
+            }
+
+            to_stream (o, i->pipe, command_to_stream::header);
+          }
+        }
+
+        if ((m & command_to_stream::here_doc) == command_to_stream::here_doc)
+        {
+          for (const expr_term& t: e)
+            to_stream (o, t.pipe, command_to_stream::here_doc);
+        }
+      }
+
+      // redirect
+      //
+      redirect::
+      redirect (redirect_type t)
+          : type (t)
+      {
+        switch (type)
+        {
+        case redirect_type::none:
+        case redirect_type::pass:
+        case redirect_type::null:
+        case redirect_type::trace:
+        case redirect_type::merge: break;
+
+        case redirect_type::here_str_literal:
+        case redirect_type::here_doc_literal: new (&str) string (); break;
+
+        case redirect_type::here_str_regex:
+        case redirect_type::here_doc_regex:
+          {
+            new (&regex) regex_lines ();
+            break;
+          }
+
+        case redirect_type::file: new (&file) file_type (); break;
+
+        case redirect_type::here_doc_ref: assert (false); break;
+        }
+      }
+
+      redirect::
+      redirect (redirect&& r)
+          : type (r.type),
+            modifiers (move (r.modifiers)),
+            end (move (r.end)),
+            end_line (r.end_line),
+            end_column (r.end_column)
+      {
+        switch (type)
+        {
+        case redirect_type::none:
+        case redirect_type::pass:
+        case redirect_type::null:
+        case redirect_type::trace: break;
+
+        case redirect_type::merge: fd = r.fd; break;
+
+        case redirect_type::here_str_literal:
+        case redirect_type::here_doc_literal:
+          {
+            new (&str) string (move (r.str));
+            break;
+          }
+        case redirect_type::here_str_regex:
+        case redirect_type::here_doc_regex:
+          {
+            new (&regex) regex_lines (move (r.regex));
+            break;
+          }
+        case redirect_type::file:
+          {
+            new (&file) file_type (move (r.file));
+            break;
+          }
+        case redirect_type::here_doc_ref:
+          {
+            new (&ref) reference_wrapper<const redirect> (r.ref);
+            break;
+          }
+        }
+      }
+
+      redirect::
+      ~redirect ()
+      {
+        switch (type)
+        {
+        case redirect_type::none:
+        case redirect_type::pass:
+        case redirect_type::null:
+        case redirect_type::trace:
+        case redirect_type::merge: break;
+
+        case redirect_type::here_str_literal:
+        case redirect_type::here_doc_literal: str.~string (); break;
+
+        case redirect_type::here_str_regex:
+        case redirect_type::here_doc_regex: regex.~regex_lines (); break;
+
+        case redirect_type::file: file.~file_type (); break;
+
+        case redirect_type::here_doc_ref:
+          {
+            ref.~reference_wrapper<const redirect> ();
+            break;
+          }
+        }
+      }
+
+      redirect& redirect::
+      operator= (redirect&& r)
+      {
+        if (this != &r)
+        {
+          this->~redirect ();
+          new (this) redirect (move (r)); // Assume noexcept move-constructor.
+        }
+        return *this;
+      }
+
+      // scope
+      //
+      scope::
+      scope (const string& id, scope* p, script* r)
+          : parent (p),
+            root (r),
+            vars (false /* global */),
+            id_path (cast<path> (assign (root->id_var) = path ())),
+            wd_path (cast<dir_path> (assign (root->wd_var) = dir_path ()))
+
+      {
+        // Construct the id_path as a string to ensure POSIX form. In fact,
+        // the only reason we keep it as a path is to be able to easily get id
+        // by calling leaf().
+        //
+        {
+          string s (p != nullptr ? p->id_path.string () : string ());
+
+          if (!s.empty () && !id.empty ())
+            s += '/';
+
+          s += id;
+          const_cast<path&> (id_path) = path (move (s));
+        }
+
+        // Calculate the working directory path unless this is the root scope
+        // (handled in an ad hoc way).
+        //
+        if (p != nullptr)
+          const_cast<dir_path&> (wd_path) = dir_path (p->wd_path) /= id;
+      }
+
+      void scope::
+      clean (cleanup c, bool implicit)
+      {
+        using std::find; // Hidden by scope::find().
+
+        assert (!implicit || c.type == cleanup_type::always);
+
+        const path& p (c.path);
+        if (!p.sub (root->wd_path))
+        {
+          if (implicit)
+            return;
+          else
+            assert (false); // Error so should have been checked.
+        }
+
+        auto pr = [&p] (const cleanup& v) -> bool {return v.path == p;};
+        auto i (find_if (cleanups.begin (), cleanups.end (), pr));
+
+        if (i == cleanups.end ())
+          cleanups.emplace_back (move (c));
+        else if (!implicit)
+          i->type = c.type;
+      }
+
+      void scope::
+      clean_special (path p)
+      {
+        special_cleanups.emplace_back (move (p));
+      }
+
+      // script_base
+      //
+      script_base::
+      script_base ()
+          : // Enter the test.* variables with the same variable types as in
+            // buildfiles except for test: while in buildfiles it can be a
+            // target name, in testscripts it should be resolved to a path.
+            //
+            // Note: entering in a custom variable pool.
+            //
+            test_var      (var_pool.insert<path> ("test")),
+            options_var   (var_pool.insert<strings> ("test.options")),
+            arguments_var (var_pool.insert<strings> ("test.arguments")),
+            redirects_var (var_pool.insert<strings> ("test.redirects")),
+            cleanups_var  (var_pool.insert<strings> ("test.cleanups")),
+
+            wd_var (var_pool.insert<dir_path> ("~")),
+            id_var (var_pool.insert<path> ("@")),
+            cmd_var (var_pool.insert<strings> ("*")),
+            cmdN_var {
+              &var_pool.insert<path> ("0"),
+              &var_pool.insert<string> ("1"),
+              &var_pool.insert<string> ("2"),
+              &var_pool.insert<string> ("3"),
+              &var_pool.insert<string> ("4"),
+              &var_pool.insert<string> ("5"),
+              &var_pool.insert<string> ("6"),
+              &var_pool.insert<string> ("7"),
+              &var_pool.insert<string> ("8"),
+              &var_pool.insert<string> ("9")} {}
+
+      // script
+      //
+      script::
+      script (const target& tt,
+              const testscript& st,
+              const dir_path& rwd)
+          : group (st.name == "testscript" ? string () : st.name, this),
+            test_target (tt),
+            target_scope (tt.base_scope ()),
+            script_target (st)
+      {
+        // Set the script working dir ($~) to $out_base/test/<id> (id_path
+        // for root is just the id which is empty if st is 'testscript').
+        //
+        const_cast<dir_path&> (wd_path) = dir_path (rwd) /= id_path.string ();
+
+        // Set the test variable at the script level. We do it even if it's
+        // set in the buildfile since they use different types.
+        //
+        {
+          value& v (assign (test_var));
+
+          // Note that the test variable's visibility is target.
+          //
+          lookup l (find_in_buildfile ("test", false));
+
+          // Note that we have similar code for simple tests.
+          //
+          const target* t (nullptr);
+
+          if (l.defined ())
+          {
+            const name* n (cast_null<name> (l));
+
+            if (n == nullptr)
+              v = nullptr;
+            else if (n->empty ())
+              v = path ();
+            else if (n->simple ())
+            {
+              // Ignore the special 'true' value.
+              //
+              if (n->value != "true")
+                v = path (n->value);
+              else
+                t = &tt;
+            }
+            else if (n->directory ())
+              v = path (n->dir);
+            else
+            {
+              // Must be a target name.
+              //
+              // @@ OUT: what if this is a @-qualified pair of names?
+              //
+              t = search_existing (*n, target_scope);
+
+              if (t == nullptr)
+                fail << "unknown target '" << *n << "' in test variable";
+            }
+          }
+          else
+            // By default we set it to the test target's path.
+            //
+            t = &tt;
+
+          // If this is a path-based target, then we use the path. If this
+          // is an alias target (e.g., dir{}), then we use the directory
+          // path. Otherwise, we leave it NULL expecting the testscript to
+          // set it to something appropriate, if used.
+          //
+          if (t != nullptr)
+          {
+            if (auto* pt = t->is_a<path_target> ())
+            {
+              // Do some sanity checks: the target better be up-to-date with
+              // an assigned path.
+              //
+              v = pt->path ();
+
+              if (v.empty ())
+                fail << "target " << *pt << " specified in the test variable "
+                     << "is out of date" <<
+                  info << "consider specifying it as a prerequisite of " << tt;
+            }
+            else if (t->is_a<alias> ())
+              v = path (t->dir);
+            else if (t != &tt)
+              fail << "target " << *t << " specified in the test variable "
+                   << "is not path-based";
+          }
+        }
+
+        // Set the special $*, $N variables.
+        //
+        reset_special ();
+      }
+
+      lookup scope::
+      find (const variable& var) const
+      {
+        // Search script scopes until we hit the root.
+        //
+        const scope* s (this);
+
+        do
+        {
+          auto p (s->vars.find (var));
+          if (p.first != nullptr)
+            return lookup (*p.first, p.second, s->vars);
+        }
+        while ((s->parent != nullptr ? (s = s->parent) : nullptr) != nullptr);
+
+        return find_in_buildfile (var.name);
+      }
+
+
+      lookup scope::
+      find_in_buildfile (const string& n, bool target_only) const
+      {
+        // Switch to the corresponding buildfile variable. Note that we don't
+        // want to insert a new variable into the pool (we might be running
+        // in parallel). Plus, if there is no such variable, then we cannot
+        // possibly find any value.
+        //
+        const variable* pvar (build2::var_pool.find (n));
+
+        if (pvar == nullptr)
+          return lookup ();
+
+        const script& s (static_cast<const script&> (*root));
+        const variable& var (*pvar);
+
+        // First check the target we are testing.
+        //
+        {
+          // Note that we skip applying the override if we did not find any
+          // value. In this case, presumably the override also affects the
+          // script target and we will pick it up there. A bit fuzzy.
+          //
+          auto p (s.test_target.find_original (var, target_only));
+
+          if (p.first)
+          {
+            if (var.overrides != nullptr)
+              p = s.target_scope.find_override (var, move (p), true);
+
+            return p.first;
+          }
+        }
+
+        // Then the script target followed by the scopes it is in. Note that
+        // while unlikely it is possible the test and script targets will be
+        // in different scopes which brings the question of which scopes we
+        // should search.
+        //
+        return s.script_target[var];
+      }
+
+      value& scope::
+      append (const variable& var)
+      {
+        lookup l (find (var));
+
+        if (l.defined () && l.belongs (*this)) // Existing var in this scope.
+          return vars.modify (l);
+
+        value& r (assign (var)); // NULL.
+
+        if (l.defined ())
+          r = *l; // Copy value (and type) from the outer scope.
+
+        return r;
+      }
+
+      void scope::
+      reset_special ()
+      {
+        // First assemble the $* value.
+        //
+        strings s;
+
+        auto append = [&s] (const strings& v)
+        {
+          s.insert (s.end (), v.begin (), v.end ());
+        };
+
+        if (lookup l = find (root->test_var))
+          s.push_back (cast<path> (l).representation ());
+
+        if (lookup l = find (root->options_var))
+          append (cast<strings> (l));
+
+        if (lookup l = find (root->arguments_var))
+          append (cast<strings> (l));
+
+        // Keep redirects/cleanups out of $N.
+        //
+        size_t n (s.size ());
+
+        if (lookup l = find (root->redirects_var))
+          append (cast<strings> (l));
+
+        if (lookup l = find (root->cleanups_var))
+          append (cast<strings> (l));
+
+        // Set the $N values if present.
+        //
+        for (size_t i (0); i <= 9; ++i)
+        {
+          value& v (assign (*root->cmdN_var[i]));
+
+          if (i < n)
+          {
+            if (i == 0)
+              v = path (s[i]);
+            else
+              v = s[i];
+          }
+          else
+            v = nullptr; // Clear any old values.
+        }
+
+        // Set $*.
+        //
+        assign (root->cmd_var) = move (s);
+      }
+    }
+  }
+}
diff --git a/libbuild2/test/script/script.hxx b/libbuild2/test/script/script.hxx
new file mode 100644
index 0000000..e3f8251
--- /dev/null
+++ b/libbuild2/test/script/script.hxx
@@ -0,0 +1,559 @@
+// file      : libbuild2/test/script/script.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_TEST_SCRIPT_SCRIPT_HXX
+#define LIBBUILD2_TEST_SCRIPT_SCRIPT_HXX
+
+#include <set>
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/variable.hxx>
+
+#include <libbuild2/test/target.hxx>
+
+#include <libbuild2/test/script/token.hxx> // replay_tokens
+
+namespace build2
+{
+  class target;
+
+  namespace test
+  {
+    namespace script
+    {
+      class parser; // Required by VC for 'friend class parser' declaration.
+
+      // Pre-parse representation.
+      //
+
+      enum class line_type
+      {
+        var,
+        cmd,
+        cmd_if,
+        cmd_ifn,
+        cmd_elif,
+        cmd_elifn,
+        cmd_else,
+        cmd_end
+      };
+
+      ostream&
+      operator<< (ostream&, line_type);
+
+      struct line
+      {
+        line_type type;
+        replay_tokens tokens;
+
+        union
+        {
+          const variable* var; // Pre-entered for line_type::var.
+        };
+      };
+
+      // Most of the time we will have just one line (test command).
+      //
+      using lines = small_vector<line, 1>;
+
+      // Parse object model.
+      //
+
+      // redirect
+      //
+      enum class redirect_type
+      {
+        none,
+        pass,
+        null,
+        trace,
+        merge,
+        here_str_literal,
+        here_str_regex,
+        here_doc_literal,
+        here_doc_regex,
+        here_doc_ref,     // Reference to here_doc literal or regex.
+        file,
+      };
+
+      // Pre-parsed (but not instantiated) regex lines. The idea here is that
+      // we should be able to re-create their (more or less) exact text
+      // representation for diagnostics but also instantiate without any
+      // re-parsing.
+      //
+      struct regex_line
+      {
+        // If regex is true, then value is the regex expression. Otherwise, it
+        // is a literal. Note that special characters can be present in both
+        // cases. For example, //+ is a regex, while /+ is a literal, both
+        // with '+' as a special character. Flags are only valid for regex.
+        // Literals falls apart into textual (has no special characters) and
+        // special (has just special characters instead) ones. For example
+        // foo is a textual literal, while /.+ is a special one. Note that
+        // literal must not have value and special both non-empty.
+        //
+        bool regex;
+
+        string value;
+        string flags;
+        string special;
+
+        uint64_t line;
+        uint64_t column;
+
+        // Create regex with optional special characters.
+        //
+        regex_line (uint64_t l, uint64_t c,
+                    string v, string f, string s = string ())
+            : regex (true),
+              value (move (v)),
+              flags (move (f)),
+              special (move (s)),
+              line (l),
+              column (c) {}
+
+        // Create a literal, either text or special.
+        //
+        regex_line (uint64_t l, uint64_t c, string v, bool s)
+            : regex (false),
+              value (s ? string () : move (v)),
+              special (s ? move (v) : string ()),
+              line (l),
+              column (c) {}
+      };
+
+      struct regex_lines
+      {
+        char intro;   // Introducer character.
+        string flags; // Global flags (here-document).
+
+        small_vector<regex_line, 8> lines;
+      };
+
+      // Output file redirect mode.
+      //
+      enum class redirect_fmode
+      {
+        compare,
+        overwrite,
+        append
+      };
+
+      struct redirect
+      {
+        redirect_type type;
+
+        struct file_type
+        {
+          using path_type = build2::path;
+          path_type path;
+          redirect_fmode mode; // Meaningless for input redirect.
+        };
+
+        union
+        {
+          int         fd;    // Merge-to descriptor.
+          string      str;   // Note: with trailing newline, if requested.
+          regex_lines regex; // Note: with trailing blank, if requested.
+          file_type   file;
+          reference_wrapper<const redirect> ref; // Note: no chains.
+        };
+
+        string modifiers;   // Redirect modifiers.
+        string end;         // Here-document end marker (no regex intro/flags).
+        uint64_t end_line;  // Here-document end marker location.
+        uint64_t end_column;
+
+        // Create redirect of a type other than reference.
+        //
+        explicit
+        redirect (redirect_type = redirect_type::none);
+
+        // Create redirect of the reference type.
+        //
+        redirect (redirect_type t, const redirect& r)
+            : type (redirect_type::here_doc_ref), ref (r)
+        {
+          // There is no support (and need) for reference chains.
+          //
+          assert (t == redirect_type::here_doc_ref &&
+                  r.type != redirect_type::here_doc_ref);
+        }
+
+        // Move constuctible/assignable-only type.
+        //
+        redirect (redirect&&);
+        redirect& operator= (redirect&&);
+
+        ~redirect ();
+
+        const redirect&
+        effective () const noexcept
+        {
+          return type == redirect_type::here_doc_ref ? ref.get () : *this;
+        }
+      };
+
+      // cleanup
+      //
+      enum class cleanup_type
+      {
+        always, // &foo  - cleanup, fail if does not exist.
+        maybe,  // &?foo - cleanup, ignore if does not exist.
+        never   // &!foo - don’t cleanup, ignore if doesn’t exist.
+      };
+
+      // File or directory to be automatically cleaned up at the end of the
+      // scope. If the path ends with a trailing slash, then it is assumed to
+      // be a directory, otherwise -- a file. A directory that is about to be
+      // cleaned up must be empty.
+      //
+      // The last component in the path may contain a wildcard that have the
+      // following semantics:
+      //
+      // dir/*   - remove all immediate files
+      // dir/*/  - remove all immediate sub-directories (must be empty)
+      // dir/**  - remove all files recursively
+      // dir/**/ - remove all sub-directories recursively (must be empty)
+      // dir/*** - remove directory dir with all files and sub-directories
+      //           recursively
+      //
+      struct cleanup
+      {
+        cleanup_type type;
+        build2::path path;
+      };
+      using cleanups = vector<cleanup>;
+
+      // command_exit
+      //
+      enum class exit_comparison {eq, ne};
+
+      struct command_exit
+      {
+        // C/C++ don't apply constraints on program exit code other than it
+        // being of type int.
+        //
+        // POSIX specifies that only the least significant 8 bits shall be
+        // available from wait() and waitpid(); the full value shall be
+        // available from waitid() (read more at _Exit, _exit Open Group
+        // spec).
+        //
+        // While the Linux man page for waitid() doesn't mention any
+        // deviations from the standard, the FreeBSD implementation (as of
+        // version 11.0) only returns 8 bits like the other wait*() calls.
+        //
+        // Windows supports 32-bit exit codes.
+        //
+        // Note that in shells some exit values can have special meaning so
+        // using them can be a source of confusion. For bash values in the
+        // [126, 255] range are such a special ones (see Appendix E, "Exit
+        // Codes With Special Meanings" in the Advanced Bash-Scripting Guide).
+        //
+        exit_comparison comparison;
+        uint8_t code;
+      };
+
+      // command
+      //
+      struct command
+      {
+        path program;
+        strings arguments;
+
+        redirect in;
+        redirect out;
+        redirect err;
+
+        script::cleanups cleanups;
+
+        command_exit exit {exit_comparison::eq, 0};
+      };
+
+      enum class command_to_stream: uint16_t
+      {
+        header   = 0x01,
+        here_doc = 0x02,              // Note: printed on a new line.
+        all      = header | here_doc
+      };
+
+      void
+      to_stream (ostream&, const command&, command_to_stream);
+
+      ostream&
+      operator<< (ostream&, const command&);
+
+      // command_pipe
+      //
+      using command_pipe = vector<command>;
+
+      void
+      to_stream (ostream&, const command_pipe&, command_to_stream);
+
+      ostream&
+      operator<< (ostream&, const command_pipe&);
+
+      // command_expr
+      //
+      enum class expr_operator {log_or, log_and};
+
+      struct expr_term
+      {
+        expr_operator op;  // OR-ed to an implied false for the first term.
+        command_pipe pipe;
+      };
+
+      using command_expr = vector<expr_term>;
+
+      void
+      to_stream (ostream&, const command_expr&, command_to_stream);
+
+      ostream&
+      operator<< (ostream&, const command_expr&);
+
+      // command_type
+      //
+      enum class command_type {test, setup, teardown};
+
+      // description
+      //
+      struct description
+      {
+        string id;
+        string summary;
+        string details;
+
+        bool
+        empty () const
+        {
+          return id.empty () && summary.empty () && details.empty ();
+        }
+      };
+
+      // scope
+      //
+      class script;
+
+      enum class scope_state {unknown, passed, failed};
+
+      class scope
+      {
+      public:
+        scope* const parent; // NULL for the root (script) scope.
+        script* const root;  // Self for the root (script) scope.
+
+        // The chain of if-else scope alternatives. See also if_cond_ below.
+        //
+        unique_ptr<scope> if_chain;
+
+        // Note that if we pass the variable name as a string, then it will
+        // be looked up in the wrong pool.
+        //
+        variable_map vars;
+
+        const path& id_path;     // Id path ($@, relative in POSIX form).
+        const dir_path& wd_path; // Working dir ($~, absolute and normalized).
+
+        optional<description> desc;
+
+        scope_state state = scope_state::unknown;
+        test::script::cleanups cleanups;
+        paths special_cleanups;
+
+        // Variables.
+        //
+      public:
+        // Lookup the variable starting from this scope, continuing with outer
+        // scopes, then the target being tested, then the testscript target,
+        // and then outer buildfile scopes (including testscript-type/pattern
+        // specific).
+        //
+        lookup
+        find (const variable&) const;
+
+        // As above but only look for buildfile variables. If target_only is
+        // false then also look in scopes of the test target (this should only
+        // be done if the variable's visibility is target).
+        //
+        lookup
+        find_in_buildfile (const string&, bool target_only = true) const;
+
+        // Return a value suitable for assignment. If the variable does not
+        // exist in this scope's map, then a new one with the NULL value is
+        // added and returned. Otherwise the existing value is returned.
+        //
+        value&
+        assign (const variable& var) {return vars.assign (var);}
+
+        // Return a value suitable for append/prepend. If the variable does
+        // not exist in this scope's map, then outer scopes are searched for
+        // the same variable. If found then a new variable with the found
+        // value is added to this scope and returned. Otherwise this function
+        // proceeds as assign() above.
+        //
+        value&
+        append (const variable&);
+
+        // Reset special $*, $N variables based on the test.* values.
+        //
+        void
+        reset_special ();
+
+        // Cleanup.
+        //
+      public:
+        // Register a cleanup. If the cleanup is explicit, then override the
+        // cleanup type if this path is already registered. Ignore implicit
+        // registration of a path outside script working directory.
+        //
+        void
+        clean (cleanup, bool implicit);
+
+        // Register cleanup of a special file. Such files are created to
+        // maintain testscript machinery and must be removed first, not to
+        // interfere with the user-defined wildcard cleanups.
+        //
+        void
+        clean_special (path p);
+
+      public:
+        virtual
+        ~scope () = default;
+
+      protected:
+        scope (const string& id, scope* parent, script* root);
+
+        // Pre-parse data.
+        //
+      public:
+        virtual bool
+        empty () const = 0;
+
+      protected:
+        friend class parser;
+
+        location start_loc_;
+        location end_loc_;
+
+        optional<line> if_cond_;
+      };
+
+      // group
+      //
+      class group: public scope
+      {
+      public:
+        vector<unique_ptr<scope>> scopes;
+
+      public:
+        group (const string& id, group& p): scope (id, &p, p.root) {}
+
+      protected:
+        group (const string& id, script* r): scope (id, nullptr, r) {}
+
+        // Pre-parse data.
+        //
+      public:
+        virtual bool
+        empty () const override
+        {
+          return
+            !if_cond_ && // The condition expression can have side-effects.
+            setup_.empty () &&
+            tdown_.empty () &&
+            find_if (scopes.begin (), scopes.end (),
+                     [] (const unique_ptr<scope>& s)
+                     {
+                       return !s->empty ();
+                     }) == scopes.end ();
+        }
+
+      private:
+        friend class parser;
+
+        lines setup_;
+        lines tdown_;
+      };
+
+      // test
+      //
+      class test: public scope
+      {
+      public:
+        test (const string& id, group& p): scope (id, &p, p.root) {}
+
+        // Pre-parse data.
+        //
+      public:
+        virtual bool
+        empty () const override
+        {
+          return tests_.empty ();
+        }
+
+      private:
+        friend class parser;
+
+        lines tests_;
+      };
+
+      // script
+      //
+      class script_base // Make sure certain things are initialized early.
+      {
+      protected:
+        script_base ();
+
+      public:
+        variable_pool var_pool;
+        mutable shared_mutex var_pool_mutex;
+
+        const variable& test_var;      // test
+        const variable& options_var;   // test.options
+        const variable& arguments_var; // test.arguments
+        const variable& redirects_var; // test.redirects
+        const variable& cleanups_var;  // test.cleanups
+
+        const variable& wd_var;       // $~
+        const variable& id_var;       // $@
+        const variable& cmd_var;      // $*
+        const variable* cmdN_var[10]; // $N
+      };
+
+      class script: public script_base, public group
+      {
+      public:
+        script (const target& test_target,
+                const testscript& script_target,
+                const dir_path& root_wd);
+
+        script (script&&) = delete;
+        script (const script&) = delete;
+        script& operator= (script&&) = delete;
+        script& operator= (const script&) = delete;
+
+      public:
+        const target&        test_target;   // Target we are testing.
+        const build2::scope& target_scope;  // Base scope of test target.
+        const testscript&    script_target; // Target of the testscript file.
+
+        // Pre-parse data.
+        //
+      private:
+        friend class parser;
+
+        // Testscript file paths. Specifically, replay_token::file points to
+        // these paths.
+        //
+        std::set<path> paths_;
+      };
+    }
+  }
+}
+
+#include <libbuild2/test/script/script.ixx>
+
+#endif // LIBBUILD2_TEST_SCRIPT_SCRIPT_HXX
diff --git a/libbuild2/test/script/script.ixx b/libbuild2/test/script/script.ixx
new file mode 100644
index 0000000..d4a216a
--- /dev/null
+++ b/libbuild2/test/script/script.ixx
@@ -0,0 +1,60 @@
+// file      : libbuild2/test/script/script.ixx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      inline command_to_stream
+      operator&= (command_to_stream& x, command_to_stream y)
+      {
+        return x = static_cast<command_to_stream> (
+          static_cast<uint16_t> (x) & static_cast<uint16_t> (y));
+      }
+
+      inline command_to_stream
+      operator|= (command_to_stream& x, command_to_stream y)
+      {
+        return x = static_cast<command_to_stream> (
+          static_cast<uint16_t> (x) | static_cast<uint16_t> (y));
+      }
+
+      inline command_to_stream
+      operator& (command_to_stream x, command_to_stream y) {return x &= y;}
+
+      inline command_to_stream
+      operator| (command_to_stream x, command_to_stream y) {return x |= y;}
+
+
+      // command
+      //
+      inline ostream&
+      operator<< (ostream& o, const command& c)
+      {
+        to_stream (o, c, command_to_stream::all);
+        return o;
+      }
+
+      // command_pipe
+      //
+      inline ostream&
+      operator<< (ostream& o, const command_pipe& p)
+      {
+        to_stream (o, p, command_to_stream::all);
+        return o;
+      }
+
+      // command_expr
+      //
+      inline ostream&
+      operator<< (ostream& o, const command_expr& e)
+      {
+        to_stream (o, e, command_to_stream::all);
+        return o;
+      }
+    }
+  }
+}
diff --git a/libbuild2/test/script/token.cxx b/libbuild2/test/script/token.cxx
new file mode 100644
index 0000000..e38e227
--- /dev/null
+++ b/libbuild2/test/script/token.cxx
@@ -0,0 +1,57 @@
+// file      : libbuild2/test/script/token.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/test/script/token.hxx>
+
+using namespace std;
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      void
+      token_printer (ostream& os, const token& t, bool d)
+      {
+        const string& v (t.value);
+
+        // Only quote non-name tokens for diagnostics.
+        //
+        const char* q (d ? "'" : "");
+
+        switch (t.type)
+        {
+        case token_type::semi:         os << q << ';'        << q; break;
+
+        case token_type::dot:          os << q << '.'        << q; break;
+
+        case token_type::plus:         os << q << '+'        << q; break;
+        case token_type::minus:        os << q << '-'        << q; break;
+
+        case token_type::clean:        os << q << '&'   << v << q; break;
+        case token_type::pipe:         os << q << '|'        << q; break;
+
+        case token_type::in_pass:      os << q << "<|"       << q; break;
+        case token_type::in_null:      os << q << "<-"       << q; break;
+        case token_type::in_str:       os << q << '<'   << v << q; break;
+        case token_type::in_doc:       os << q << "<<"  << v << q; break;
+        case token_type::in_file:      os << q << "<<<"      << q; break;
+
+        case token_type::out_pass:     os << q << ">|"       << q; break;
+        case token_type::out_null:     os << q << ">-"       << q; break;
+        case token_type::out_trace:    os << q << ">!"       << q; break;
+        case token_type::out_merge:    os << q << ">&"       << q; break;
+        case token_type::out_str:      os << q << '>'   << v << q; break;
+        case token_type::out_doc:      os << q << ">>"  << v << q; break;
+        case token_type::out_file_cmp: os << q << ">>>" << v << q; break;
+        case token_type::out_file_ovr: os << q << ">="  << v << q; break;
+        case token_type::out_file_app: os << q << ">+"  << v << q; break;
+
+        default: build2::token_printer (os, t, d);
+        }
+      }
+    }
+  }
+}
diff --git a/libbuild2/test/script/token.hxx b/libbuild2/test/script/token.hxx
new file mode 100644
index 0000000..4abe617
--- /dev/null
+++ b/libbuild2/test/script/token.hxx
@@ -0,0 +1,65 @@
+// file      : libbuild2/test/script/token.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_TEST_SCRIPT_TOKEN_HXX
+#define LIBBUILD2_TEST_SCRIPT_TOKEN_HXX
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/token.hxx>
+
+namespace build2
+{
+  namespace test
+  {
+    namespace script
+    {
+      struct token_type: build2::token_type
+      {
+        using base_type = build2::token_type;
+
+        enum
+        {
+          // NOTE: remember to update token_printer()!
+
+          semi = base_type::value_next, // ;
+
+          dot,                          // .
+
+          plus,                         // +
+          minus,                        // -
+
+          pipe,                         // |
+          clean,                        // &{?!}   (modifiers in value)
+
+          in_pass,                      // <|
+          in_null,                      // <-
+          in_str,                       // <{:}    (modifiers in value)
+          in_doc,                       // <<{:}   (modifiers in value)
+          in_file,                      // <<<
+
+          out_pass,                     // >|
+          out_null,                     // >-
+          out_trace,                    // >!
+          out_merge,                    // >&
+          out_str,                      // >{:~}   (modifiers in value)
+          out_doc,                      // >>{:~}  (modifiers in value)
+          out_file_cmp,                 // >>>
+          out_file_ovr,                 // >=
+          out_file_app                  // >+
+        };
+
+        token_type () = default;
+        token_type (value_type v): base_type (v) {}
+        token_type (base_type v): base_type (v) {}
+      };
+
+      void
+      token_printer (ostream&, const token&, bool);
+    }
+  }
+}
+
+#endif // LIBBUILD2_TEST_SCRIPT_TOKEN_HXX
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