>From 0a74257b9fb7e02587b6c5553d8bc1b536249a7e Mon Sep 17 00:00:00 2001
From: Colin Watson <address@hidden>
Date: Sun, 27 Aug 2017 08:16:21 +0100
Subject: [PATCH] env: add --chdir option

This is useful when chaining with other commands that run commands in a
different context.

* NEWS (New features): Document the new option.
* doc/coreutils.texi (env invocation): Likewise.
* src/env.c (usage): Likewise.
(main): Implement the new option.
* tests/misc/env.sh: Test the new option.
---
 NEWS               |  3 +++
 doc/coreutils.texi | 17 +++++++++++++++++
 src/env.c          | 20 ++++++++++++++++++++
 tests/misc/env.sh  | 10 +++++++++-
 4 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index d37195e..60d5ca5 100644
--- a/NEWS
+++ b/NEWS
@@ -86,6 +86,9 @@ GNU coreutils NEWS                                    -*- outline -*-
 
   expr supports multibyte strings for all string operations.
 
+  env now has a --chdir option to change to a new working directory before
+  executing the subsidiary program.
+
 ** Improvements
 
   mv --verbose now distinguishes rename and copy operations.
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 8f1cb4c..f127517 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -16909,6 +16909,23 @@ environment.
 @opindex --ignore-environment
 Start with an empty environment, ignoring the inherited environment.
 
+@item --chdir=@var{dir}
+@opindex --chdir
+Change the working directory to @var{dir} before invoking @var{command}.
+This differs from the shell built-in @command{cd} in that it starts
+@var{command} as a subprocess rather than altering the shell's own working
+directory; this allows it to be chained with other commands that run commands
+in a different context.  For example:
+
+@example
+# Run 'true' with /chroot as its root directory and /srv as its working
+# directory.
+chroot /chroot env --chdir=/srv true
+# Run 'true' with /build as its working directory, FOO=bar in its
+# environment, and a time limit of five seconds.
+env --chdir=/build FOO=bar timeout 5 true
+@end example
+
 @end table
 
 @cindex exit status of @command{env}
diff --git a/src/env.c b/src/env.c
index 63d5c2c..291fbb4 100644
--- a/src/env.c
+++ b/src/env.c
@@ -33,11 +33,19 @@
   proper_name ("Richard Mlynarik"), \
   proper_name ("David MacKenzie")
 
+/* For long options that have no equivalent short option, use a
+   non-character as a pseudo short option, starting with CHAR_MAX + 1.  */
+enum
+{
+  CHDIR = CHAR_MAX + 1
+};
+
 static struct option const longopts[] =
 {
   {"ignore-environment", no_argument, NULL, 'i'},
   {"null", no_argument, NULL, '0'},
   {"unset", required_argument, NULL, 'u'},
+  {"chdir", required_argument, NULL, CHDIR},
   {GETOPT_HELP_OPTION_DECL},
   {GETOPT_VERSION_OPTION_DECL},
   {NULL, 0, NULL, 0}
@@ -63,6 +71,7 @@ Set each NAME to VALUE in the environment and run COMMAND.\n\
   -i, --ignore-environment  start with an empty environment\n\
   -0, --null           end each output line with NUL, not newline\n\
   -u, --unset=NAME     remove variable from the environment\n\
+      --chdir=DIR      change working directory to DIR\n\
 "), stdout);
       fputs (HELP_OPTION_DESCRIPTION, stdout);
       fputs (VERSION_OPTION_DESCRIPTION, stdout);
@@ -81,6 +90,7 @@ main (int argc, char **argv)
   int optc;
   bool ignore_environment = false;
   bool opt_nul_terminate_output = false;
+  char const *newdir = NULL;
 
   initialize_main (&argc, &argv);
   set_program_name (argv[0]);
@@ -103,6 +113,9 @@ main (int argc, char **argv)
         case '0':
           opt_nul_terminate_output = true;
           break;
+	case CHDIR:
+	  newdir = optarg;
+	  break;
         case_GETOPT_HELP_CHAR;
         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
         default:
@@ -154,6 +167,13 @@ main (int argc, char **argv)
       usage (EXIT_CANCELED);
     }
 
+  if (newdir)
+    {
+      if (chdir (newdir) != 0)
+	die (EXIT_CANCELED, errno, _("cannot change directory to %s"),
+	     quoteaf (newdir));
+    }
+
   execvp (argv[optind], &argv[optind]);
 
   int exit_status = errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE;
diff --git a/tests/misc/env.sh b/tests/misc/env.sh
index f2f6ba8..c409630 100755
--- a/tests/misc/env.sh
+++ b/tests/misc/env.sh
@@ -18,7 +18,7 @@
 
 
 . "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
-print_ver_ env
+print_ver_ env pwd
 
 # A simple shebang program to call "echo" from symlinks like "./-u" or "./--".
 echo "#!$abs_top_builddir/src/echo simple_echo" > simple_echo \
@@ -150,4 +150,12 @@ test "x$(sh -c '\c=d echo fail')" = xpass && #dash 0.5.4 fails so check first
 returns_ 125 env -u a=b true || fail=1
 returns_ 125 env -u '' true || fail=1
 
+# Verify changing directory.
+mkdir empty || framework_failure_
+returns_ 125 env --chdir=empty/nonexistent true || fail=1
+curdir=$(env pwd) || fail=1
+test "$curdir" = "$(pwd)" || fail=1
+curdir=$(env --chdir=empty pwd) || fail=1
+test "$curdir" = "$(cd empty && pwd)" || fail=1
+
 Exit $fail
-- 
2.7.4