spack env command

spack env allows regular commands to be run with a spack build environment.
It also displays the spack build environment for a package.

lib/spack/spack/cmd/env.py

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+##############################################################################
+# Copyright (c) 2013, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Written by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://scalability-llnl.github.io/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License (as published by
+# the Free Software Foundation) version 2.1 dated February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this program; if not, write to the Free Software Foundation,
+# Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+import os
+from external import argparse
+import llnl.util.tty as tty
+import spack.cmd
+import spack.build_environment as build_env
+
+description = "Run a command with the environment for a particular spec's install."
+
+def setup_parser(subparser):
+    subparser.add_argument(
+        'spec', nargs=argparse.REMAINDER, help="specs of package environment to emulate.")
+
+
+def env(parser, args):
+    if not args.spec:
+        tty.die("spack env requires a spec.")
+
+    # Specs may have spaces in them, so if they do, require that the
+    # caller put a '--' between the spec and the command to be
+    # executed.  If there is no '--', assume that the spec is the
+    # first argument.
+    sep = '--'
+    if sep in args.spec:
+        s = args.spec.index(sep)
+        spec = args.spec[:s]
+        cmd  = args.spec[s+1:]
+    else:
+        spec = args.spec[0]
+        cmd  = args.spec[1:]
+
+    specs = spack.cmd.parse_specs(spec, concretize=True)
+    if len(specs) > 1:
+        tty.die("spack env only takes one spec.")
+    spec = specs[0]
+
+    build_env.setup_package(spec.package)
+
+    if not cmd:
+        # If no command act like the "env" command and print out env vars.
+        for key, val in os.environ.items():
+            print "%s=%s" % (key, val)
+
+    else:
+        # Otherwise execute the command with the new environment
+        os.execvp(cmd[0], cmd)