src/env.c

   1 /* env - run a program in a modified environment
   2    Copyright (C) 86, 91, 92, 93, 94, 95, 1996 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
  89 int putenv ();
  90
  91 static void usage __P ((int status));
  92
  93 extern char **environ;
  94
  95 /* The name by which this program was run. */
  96 char *program_name;
  97
  98 /* If nonzero, display usage information and exit.  */
  99 static int show_help;
 100
 101 /* If nonzero, print the version on standard output and exit.  */
 102 static int show_version;
 103
 104 static struct option const longopts[] =
 105 {
 106   {"help", no_argument, &show_help, 1},
 107   {"ignore-environment", no_argument, NULL, 'i'},
 108   {"unset", required_argument, NULL, 'u'},
 109   {"version", no_argument, &show_version, 1},
 110   {NULL, 0, NULL, 0}
 111 };
 112
 113 int
 114 main (register int argc, register char **argv, char **envp)
 115 {
 116   char *dummy_environ[1];
 117   int optc;
 118   int ignore_environment = 0;
 119
 120   program_name = argv[0];
 121   setlocale (LC_ALL, "");
 122   bindtextdomain (PACKAGE, LOCALEDIR);
 123   textdomain (PACKAGE);
 124
 125   while ((optc = getopt_long (argc, argv, "+iu:", longopts, (int *) 0)) != EOF)
 126     {
 127       switch (optc)
 128         {
 129         case 0:
 130           break;
 131         case 'i':
 132           ignore_environment = 1;
 133           break;
 134         case 'u':
 135           break;
 136         default:
 137           usage (2);
 138         }
 139     }
 140
 141   if (show_version)
 142     {
 143       printf ("env - %s\n", PACKAGE_VERSION);
 144       exit (0);
 145     }
 146
 147   if (show_help)
 148     usage (0);
 149
 150   if (optind != argc && !strcmp (argv[optind], "-"))
 151     ignore_environment = 1;
 152
 153   environ = dummy_environ;
 154   environ[0] = NULL;
 155
 156   if (!ignore_environment)
 157     for (; *envp; envp++)
 158       putenv (*envp);
 159
 160   optind = 0;                   /* Force GNU getopt to re-initialize. */
 161   while ((optc = getopt_long (argc, argv, "+iu:", longopts, (int *) 0)) != EOF)
 162     if (optc == 'u')
 163       putenv (optarg);          /* Requires GNU putenv. */
 164
 165   if (optind != argc && !strcmp (argv[optind], "-"))
 166     ++optind;
 167
 168   while (optind < argc && strchr (argv[optind], '='))
 169     putenv (argv[optind++]);
 170
 171   /* If no program is specified, print the environment and exit. */
 172   if (optind == argc)
 173     {
 174       while (*environ)
 175         puts (*environ++);
 176       exit (0);
 177     }
 178
 179   execvp (argv[optind], &argv[optind]);
 180   error (errno == ENOENT ? 127 : 126, errno, "%s", argv[optind]);
 181 }
 182
 183 static void
 184 usage (int status)
 185 {
 186   if (status != 0)
 187     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 188              program_name);
 189   else
 190     {
 191       printf (_("\
 192 Usage: %s [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n"),
 193               program_name);
 194       printf (_("\
 195 Set each NAME to VALUE in the environment and run COMMAND.\n\
 196 \n\
 197   -u, --unset=NAME           remove variable from the environment\n\
 198   -i, --ignore-environment   start with an empty environment\n\
 199       --help                 display this help and exit\n\
 200       --version              output version information and exit\n\
 201 \n\
 202 A mere - implies -i.  If no COMMAND, print the resulting environment.\n\
 203 "));
 204     }
 205   exit (status);
 206 }