1 /* env - run a program in a modified environment
2 Copyright (C) 1986, 1991-2005, 2007 Free Software Foundation, Inc.
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.
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.
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/>. */
17 /* Richard Mlynarik and David MacKenzie */
23 Construct a new environment from scratch; normally the
24 environment is inherited from the parent process, except as
25 modified by other options.
29 Unset variable VARIABLE (remove it from the environment).
30 If VARIABLE was not set, does nothing.
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.
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 "=".
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.
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".
53 If the environment passed to "env" is
54 { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
57 runs "foo" in a null environment.
60 runs "foo" in the environment
61 { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
63 env DISPLAY=gnu:0 nemacs
64 runs "nemacs" in the environment
65 { LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks DISPLAY=gnu:0 }
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
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 }
82 #include <sys/types.h>
88 /* The official name of this program (e.g., no `g' prefix). */
89 #define PROGRAM_NAME "env"
91 #define AUTHORS "Richard Mlynarik", "David MacKenzie"
95 extern char **environ;
97 /* The name by which this program was run. */
100 static struct option const longopts[] =
102 {"ignore-environment", no_argument, NULL, 'i'},
103 {"unset", required_argument, NULL, 'u'},
104 {GETOPT_HELP_OPTION_DECL},
105 {GETOPT_VERSION_OPTION_DECL},
112 if (status != EXIT_SUCCESS)
113 fprintf (stderr, _("Try `%s --help' for more information.\n"),
118 Usage: %s [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]\n"),
121 Set each NAME to VALUE in the environment and run COMMAND.\n\
123 -i, --ignore-environment start with an empty environment\n\
124 -u, --unset=NAME remove variable from the environment\n\
126 fputs (HELP_OPTION_DESCRIPTION, stdout);
127 fputs (VERSION_OPTION_DESCRIPTION, stdout);
130 A mere - implies -i. If no COMMAND, print the resulting environment.\n\
132 emit_bug_reporting_address ();
138 main (int argc, char **argv)
141 bool ignore_environment = false;
143 initialize_main (&argc, &argv);
144 program_name = argv[0];
145 setlocale (LC_ALL, "");
146 bindtextdomain (PACKAGE, LOCALEDIR);
147 textdomain (PACKAGE);
149 initialize_exit_failure (EXIT_FAIL);
150 atexit (close_stdout);
152 while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
157 ignore_environment = true;
161 case_GETOPT_HELP_CHAR;
162 case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
168 if (optind < argc && STREQ (argv[optind], "-"))
169 ignore_environment = true;
171 if (ignore_environment)
173 static char *dummy_environ[] = { NULL };
174 environ = dummy_environ;
177 optind = 0; /* Force GNU getopt to re-initialize. */
178 while ((optc = getopt_long (argc, argv, "+iu:", longopts, NULL)) != -1)
180 putenv (optarg); /* Requires GNU putenv. */
182 if (optind < argc && STREQ (argv[optind], "-"))
185 while (optind < argc && strchr (argv[optind], '='))
186 putenv (argv[optind++]);
188 /* If no program is specified, print the environment and exit. */
191 char *const *e = environ;
197 execvp (argv[optind], &argv[optind]);
200 int exit_status = (errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE);
201 error (0, errno, "%s", argv[optind]);