src/env.c

   1 /* env - run a program in a modified environment
   2    Copyright (C) 1986, 1991-2005, 2007-2009 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 <sys/types.h>
  82 #include <getopt.h>
  83
  84 #include "system.h"
  85 #include "error.h"
  86
  87 /* The official name of this program (e.g., no `g' prefix).  */
  88 #define PROGRAM_NAME "env"
  89
  90 #define AUTHORS \
  91   proper_name ("Richard Mlynarik"), \
  92   proper_name ("David MacKenzie")
  93
  94 extern char **environ;
  95
  96 static struct option const longopts[] =
  97 {
  98   {"ignore-environment", no_argument, NULL, 'i'},
  99   {"unset", required_argument, NULL, 'u'},
 100   {GETOPT_HELP_OPTION_DECL},
 101   {GETOPT_VERSION_OPTION_DECL},
 102   {NULL, 0, NULL, 0}
 103 };
 104
 105 void
 106 usage (int status)
 107 {
 108   if (status != EXIT_SUCCESS)
 109     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 110              program_name);
 111   else
 112     {
 113       printf (_("\
 114 Usage: %s [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n"),
 115               program_name);
 116       fputs (_("\
 117 Set each NAME to VALUE in the environment and run COMMAND.\n\
 118 \n\
 119   -i, --ignore-environment   start with an empty environment\n\
 120   -u, --unset=NAME           remove variable from the environment\n\
 121 "), stdout);
 122       fputs (HELP_OPTION_DESCRIPTION, stdout);
 123       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 124       fputs (_("\
 125 \n\
 126 A mere - implies -i.  If no COMMAND, print the resulting environment.\n\
 127 "), stdout);
 128       emit_ancillary_info ();
 129     }
 130   exit (status);
 131 }
 132
 133 int
 134 main (int argc, char **argv)
 135 {
 136   int optc;
 137   bool ignore_environment = false;
 138
 139   initialize_main (&argc, &argv);
 140   set_program_name (argv[0]);
 141   setlocale (LC_ALL, "");
 142   bindtextdomain (PACKAGE, LOCALEDIR);
 143   textdomain (PACKAGE);
 144
 145   initialize_exit_failure (EXIT_CANCELED);
 146   atexit (close_stdout);
 147
 148   while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
 149     {
 150       switch (optc)
 151         {
 152         case 'i':
 153           ignore_environment = true;
 154           break;
 155         case 'u':
 156           break;
 157         case_GETOPT_HELP_CHAR;
 158         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 159         default:
 160           usage (EXIT_CANCELED);
 161         }
 162     }
 163
 164   if (optind < argc && STREQ (argv[optind], "-"))
 165     ignore_environment = true;
 166
 167   if (ignore_environment)
 168     {
 169       static char *dummy_environ[] = { NULL };
 170       environ = dummy_environ;
 171     }
 172
 173   optind = 0;                   /* Force GNU getopt to re-initialize. */
 174   while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
 175     if (optc == 'u')
 176       putenv (optarg);          /* Requires GNU putenv. */
 177
 178   if (optind < argc && STREQ (argv[optind], "-"))
 179     ++optind;
 180
 181   while (optind < argc && strchr (argv[optind], '='))
 182     putenv (argv[optind++]);
 183
 184   /* If no program is specified, print the environment and exit. */
 185   if (argc <= optind)
 186     {
 187       char *const *e = environ;
 188       while (*e)
 189         puts (*e++);
 190       exit (EXIT_SUCCESS);
 191     }
 192
 193   execvp (argv[optind], &argv[optind]);
 194
 195   {
 196     int exit_status = (errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE);
 197     error (0, errno, "%s", argv[optind]);
 198     exit (exit_status);
 199   }
 200 }