src/env.c

   1 /* env - run a program in a modified environment
   2    Copyright (C) 1986, 1991-2005, 2007 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* Richard Mlynarik and David MacKenzie */
  18
  19 /* Options:
  20    -
  21    -i
  22    --ignore-environment
  23         Construct a new environment from scratch; normally the
  24         environment is inherited from the parent process, except as
  25         modified by other options.
  26
  27    -u variable
  28    --unset=variable
  29         Unset variable VARIABLE (remove it from the environment).
  30         If VARIABLE was not set, does nothing.
  31
  32    variable=value (an arg containing a "=" character)
  33         Set the environment variable VARIABLE to value VALUE.  VALUE
  34         may be of zero length ("variable=").  Setting a variable to a
  35         zero-length value is different from unsetting it.
  36
  37    --
  38         Indicate that the following argument is the program
  39         to invoke.  This is necessary when the program's name
  40         begins with "-" or contains a "=".
  41
  42    The first remaining argument specifies a program to invoke;
  43    it is searched for according to the specification of the PATH
  44    environment variable.  Any arguments following that are
  45    passed as arguments to that program.
  46
  47    If no command name is specified following the environment
  48    specifications, the resulting environment is printed.
  49    This is like specifying a command name of "printenv".
  50
  51    Examples:
  52
  53    If the environment passed to "env" is
  54         { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
  55
  56    env - foo
  57         runs "foo" in a null environment.
  58
  59    env foo
  60         runs "foo" in the environment
  61         { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
  62
  63    env DISPLAY=gnu:0 nemacs
  64         runs "nemacs" in the environment
  65         { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks DISPLAY=gnu:0 }
  66
  67    env - LOGNAME=foo /hacks/hack bar baz
  68         runs the "hack" program on arguments "bar" and "baz" in an
  69         environment in which the only variable is "LOGNAME".  Note that
  70         the "-" option clears out the PATH variable, so one should be
  71         careful to specify in which directory to find the program to
  72         call.
  73
  74    env -u EDITOR LOGNAME=foo PATH=/energy -- e=mc2 bar baz
  75         runs the program "/energy/e=mc2" with environment
  76         { LOGNAME=foo PATH=/energy }
  77 */
  78
  79 #include <config.h>
  80 #include <stdio.h>
  81 #include <getopt.h>
  82 #include <sys/types.h>
  83 #include <getopt.h>
  84
  85 #include "system.h"
  86 #include "error.h"
  87
  88 /* The official name of this program (e.g., no `g' prefix).  */
  89 #define PROGRAM_NAME "env"
  90
  91 #define AUTHORS "Richard Mlynarik", "David MacKenzie"
  92
  93 int putenv ();
  94
  95 extern char **environ;
  96
  97 /* The name by which this program was run. */
  98 char *program_name;
  99
 100 static struct option const longopts[] =
 101 {
 102   {"ignore-environment", no_argument, NULL, 'i'},
 103   {"unset", required_argument, NULL, 'u'},
 104   {GETOPT_HELP_OPTION_DECL},
 105   {GETOPT_VERSION_OPTION_DECL},
 106   {NULL, 0, NULL, 0}
 107 };
 108
 109 void
 110 usage (int status)
 111 {
 112   if (status != EXIT_SUCCESS)
 113     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 114              program_name);
 115   else
 116     {
 117       printf (_("\
 118 Usage: %s [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n"),
 119               program_name);
 120       fputs (_("\
 121 Set each NAME to VALUE in the environment and run COMMAND.\n\
 122 \n\
 123   -i, --ignore-environment   start with an empty environment\n\
 124   -u, --unset=NAME           remove variable from the environment\n\
 125 "), stdout);
 126       fputs (HELP_OPTION_DESCRIPTION, stdout);
 127       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 128       fputs (_("\
 129 \n\
 130 A mere - implies -i.  If no COMMAND, print the resulting environment.\n\
 131 "), stdout);
 132       emit_bug_reporting_address ();
 133     }
 134   exit (status);
 135 }
 136
 137 int
 138 main (int argc, char **argv)
 139 {
 140   int optc;
 141   bool ignore_environment = false;
 142
 143   initialize_main (&argc, &argv);
 144   program_name = argv[0];
 145   setlocale (LC_ALL, "");
 146   bindtextdomain (PACKAGE, LOCALEDIR);
 147   textdomain (PACKAGE);
 148
 149   initialize_exit_failure (EXIT_FAILURE);
 150   atexit (close_stdout);
 151
 152   while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
 153     {
 154       switch (optc)
 155         {
 156         case 'i':
 157           ignore_environment = true;
 158           break;
 159         case 'u':
 160           break;
 161         case_GETOPT_HELP_CHAR;
 162         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 163         default:
 164           usage (EXIT_FAILURE);
 165         }
 166     }
 167
 168   if (optind < argc && STREQ (argv[optind], "-"))
 169     ignore_environment = true;
 170
 171   if (ignore_environment)
 172     {
 173       static char *dummy_environ[] = { NULL };
 174       environ = dummy_environ;
 175     }
 176
 177   optind = 0;                   /* Force GNU getopt to re-initialize. */
 178   while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
 179     if (optc == 'u')
 180       putenv (optarg);          /* Requires GNU putenv. */
 181
 182   if (optind < argc && STREQ (argv[optind], "-"))
 183     ++optind;
 184
 185   while (optind < argc && strchr (argv[optind], '='))
 186     putenv (argv[optind++]);
 187
 188   /* If no program is specified, print the environment and exit. */
 189   if (argc <= optind)
 190     {
 191       char *const *e = environ;
 192       while (*e)
 193         puts (*e++);
 194       exit (EXIT_SUCCESS);
 195     }
 196
 197   execvp (argv[optind], &argv[optind]);
 198
 199   {
 200     int exit_status = (errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE);
 201     error (0, errno, "%s", argv[optind]);
 202     exit (exit_status);
 203   }
 204 }