src/env.c

   1 /* env - run a program in a modified environment
   2    Copyright (C) 1986, 1991-2005 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 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 environment
  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
  89 /* The official name of this program (e.g., no `g' prefix).  */
  90 #define PROGRAM_NAME "env"
  91
  92 #define AUTHORS "Richard Mlynarik", "David MacKenzie"
  93
  94 int putenv ();
  95
  96 extern char **environ;
  97
  98 /* The name by which this program was run. */
  99 char *program_name;
 100
 101 static struct option const longopts[] =
 102 {
 103   {"ignore-environment", no_argument, NULL, 'i'},
 104   {"unset", required_argument, NULL, 'u'},
 105   {GETOPT_HELP_OPTION_DECL},
 106   {GETOPT_VERSION_OPTION_DECL},
 107   {NULL, 0, NULL, 0}
 108 };
 109
 110 void
 111 usage (int status)
 112 {
 113   if (status != EXIT_SUCCESS)
 114     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 115              program_name);
 116   else
 117     {
 118       printf (_("\
 119 Usage: %s [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n"),
 120               program_name);
 121       fputs (_("\
 122 Set each NAME to VALUE in the environment and run COMMAND.\n\
 123 \n\
 124   -i, --ignore-environment   start with an empty environment\n\
 125   -u, --unset=NAME           remove variable from the environment\n\
 126 "), stdout);
 127       fputs (HELP_OPTION_DESCRIPTION, stdout);
 128       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 129       fputs (_("\
 130 \n\
 131 A mere - implies -i.  If no COMMAND, print the resulting environment.\n\
 132 "), stdout);
 133       printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
 134     }
 135   exit (status);
 136 }
 137
 138 int
 139 main (int argc, char **argv)
 140 {
 141   int optc;
 142   bool ignore_environment = false;
 143
 144   initialize_main (&argc, &argv);
 145   program_name = argv[0];
 146   setlocale (LC_ALL, "");
 147   bindtextdomain (PACKAGE, LOCALEDIR);
 148   textdomain (PACKAGE);
 149
 150   initialize_exit_failure (EXIT_FAIL);
 151   atexit (close_stdout);
 152
 153   while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
 154     {
 155       switch (optc)
 156         {
 157         case 'i':
 158           ignore_environment = true;
 159           break;
 160         case 'u':
 161           break;
 162         case_GETOPT_HELP_CHAR;
 163         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 164         default:
 165           usage (EXIT_FAIL);
 166         }
 167     }
 168
 169   if (optind < argc && STREQ (argv[optind], "-"))
 170     ignore_environment = true;
 171
 172   if (ignore_environment)
 173     {
 174       static char *dummy_environ[] = { NULL };
 175       environ = dummy_environ;
 176     }
 177
 178   optind = 0;                   /* Force GNU getopt to re-initialize. */
 179   while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
 180     if (optc == 'u')
 181       putenv (optarg);          /* Requires GNU putenv. */
 182
 183   if (optind < argc && STREQ (argv[optind], "-"))
 184     ++optind;
 185
 186   while (optind < argc && strchr (argv[optind], '='))
 187     putenv (argv[optind++]);
 188
 189   /* If no program is specified, print the environment and exit. */
 190   if (argc <= optind)
 191     {
 192       while (*environ)
 193         puts (*environ++);
 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 }