src/env.c

   1 /* env - run a program in a modified environment
   2    Copyright (C) 1986, 1991-2001 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 2, or (at your option)
   7    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, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Richard Mlynarik and David MacKenzie */
  19
  20 /* Options:
  21    -
  22    -i
  23    --ignore-environment
  24         Construct a new environment from scratch; normally the
  25         environment is inherited from the parent process, except as
  26         modified by other options.
  27
  28    -u variable
  29    --unset=variable
  30         Unset variable VARIABLE (remove it from the environment).
  31         If VARIABLE was not set, does nothing.
  32
  33    variable=value (an arg containing a "=" character)
  34         Set the environment variable VARIABLE to value VALUE.  VALUE
  35         may be of zero length ("variable=").  Setting a variable to a
  36         zero-length value is different from unsetting it.
  37
  38    --
  39         Indicate that the following argument is the program
  40         to invoke.  This is necessary when the program's name
  41         begins with "-" or contains a "=".
  42
  43    The first remaining argument specifies a program to invoke;
  44    it is searched for according to the specification of the PATH
  45    environment variable.  Any arguments following that are
  46    passed as arguments to that program.
  47
  48    If no command name is specified following the environment
  49    specifications, the resulting environment is printed.
  50    This is like specifying a command name of "printenv".
  51
  52    Examples:
  53
  54    If the environment passed to "env" is
  55         { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
  56
  57    env - foo
  58         runs "foo" in a null environment.
  59
  60    env foo
  61         runs "foo" in the environment
  62         { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
  63
  64    env DISPLAY=gnu:0 nemacs
  65         runs "nemacs" in the envionment
  66         { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks DISPLAY=gnu:0 }
  67
  68    env - LOGNAME=foo /hacks/hack bar baz
  69         runs the "hack" program on arguments "bar" and "baz" in an
  70         environment in which the only variable is "LOGNAME".  Note that
  71         the "-" option clears out the PATH variable, so one should be
  72         careful to specify in which directory to find the program to
  73         call.
  74
  75    env -u EDITOR LOGNAME=foo PATH=/energy -- e=mc2 bar baz
  76         runs the program "/energy/e=mc2" with environment
  77         { LOGNAME=foo PATH=/energy }
  78 */
  79
  80 #include <config.h>
  81 #include <stdio.h>
  82 #include <getopt.h>
  83 #include <sys/types.h>
  84 #include <getopt.h>
  85
  86 #include "system.h"
  87 #include "error.h"
  88 #include "closeout.h"
  89
  90 /* The official name of this program (e.g., no `g' prefix).  */
  91 #define PROGRAM_NAME "env"
  92
  93 #define AUTHORS N_ ("Richard Mlynarik and David MacKenzie")
  94
  95 int putenv ();
  96
  97 extern char **environ;
  98
  99 /* The name by which this program was run. */
 100 char *program_name;
 101
 102 static struct option const longopts[] =
 103 {
 104   {"ignore-environment", no_argument, NULL, 'i'},
 105   {"unset", required_argument, NULL, 'u'},
 106   {GETOPT_HELP_OPTION_DECL},
 107   {GETOPT_VERSION_OPTION_DECL},
 108   {NULL, 0, NULL, 0}
 109 };
 110
 111 void
 112 usage (int status)
 113 {
 114   if (status != 0)
 115     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 116              program_name);
 117   else
 118     {
 119       printf (_("\
 120 Usage: %s [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n"),
 121               program_name);
 122       fputs (_("\
 123 Set each NAME to VALUE in the environment and run COMMAND.\n\
 124 \n\
 125   -i, --ignore-environment   start with an empty environment\n\
 126   -u, --unset=NAME           remove variable from the environment\n\
 127 "), stdout);
 128       fputs (HELP_OPTION_DESCRIPTION, stdout);
 129       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 130       fputs (_("\
 131 \n\
 132 A mere - implies -i.  If no COMMAND, print the resulting environment.\n\
 133 "), stdout);
 134       printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
 135     }
 136   exit (status);
 137 }
 138
 139 int
 140 main (register int argc, register char **argv, char **envp)
 141 {
 142   char *dummy_environ[1];
 143   int optc;
 144   int ignore_environment = 0;
 145
 146   program_name = argv[0];
 147   setlocale (LC_ALL, "");
 148   bindtextdomain (PACKAGE, LOCALEDIR);
 149   textdomain (PACKAGE);
 150
 151   atexit (close_stdout);
 152
 153   while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
 154     {
 155       switch (optc)
 156         {
 157         case 0:
 158           break;
 159         case 'i':
 160           ignore_environment = 1;
 161           break;
 162         case 'u':
 163           break;
 164         case_GETOPT_HELP_CHAR;
 165         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 166         default:
 167           usage (2);
 168         }
 169     }
 170
 171   if (optind != argc && !strcmp (argv[optind], "-"))
 172     ignore_environment = 1;
 173
 174   environ = dummy_environ;
 175   environ[0] = NULL;
 176
 177   if (!ignore_environment)
 178     for (; *envp; envp++)
 179       putenv (*envp);
 180
 181   optind = 0;                   /* Force GNU getopt to re-initialize. */
 182   while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
 183     if (optc == 'u')
 184       putenv (optarg);          /* Requires GNU putenv. */
 185
 186   if (optind != argc && !strcmp (argv[optind], "-"))
 187     ++optind;
 188
 189   while (optind < argc && strchr (argv[optind], '='))
 190     putenv (argv[optind++]);
 191
 192   /* If no program is specified, print the environment and exit. */
 193   if (optind == argc)
 194     {
 195       while (*environ)
 196         puts (*environ++);
 197       exit (0);
 198     }
 199
 200   execvp (argv[optind], &argv[optind]);
 201
 202   {
 203     int exit_status = (errno == ENOENT ? 127 : 126);
 204     error (0, errno, "%s", argv[optind]);
 205     exit (exit_status);
 206   }
 207 }