1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
/* env - run a program in a modified environment
Copyright (C) 1986, 1991 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/* Richard Mlynarik and David MacKenzie */
/* Options:
-
-i
--ignore-environment
Construct a new environment from scratch; normally the
environment is inherited from the parent process, except as
modified by other options.
-u variable
--unset=variable
Unset variable VARIABLE (remove it from the environment).
If VARIABLE was not set, does nothing.
variable=value (an arg containing a "=" character)
Set the environment variable VARIABLE to value VALUE. VALUE
may be of zero length ("variable="). Setting a variable to a
zero-length value is different from unsetting it.
--
Indicate that the following argument is the program
to invoke. This is necessary when the program's name
begins with "-" or contains a "=".
The first remaining argument specifies a program to invoke;
it is searched for according to the specification of the PATH
environment variable. Any arguments following that are
passed as arguments to that program.
If no command name is specified following the environment
specifications, the resulting environment is printed.
This is like specifying a command name of "printenv".
Examples:
If the environment passed to "env" is
{ LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
env - foo
runs "foo" in a null environment.
env foo
runs "foo" in the environment
{ LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks }
env DISPLAY=gnu:0 nemacs
runs "nemacs" in the envionment
{ LOGNAME=rms EDITOR=emacs PATH=.:/gnubin:/hacks DISPLAY=gnu:0 }
env - LOGNAME=foo /hacks/hack bar baz
runs the "hack" program on arguments "bar" and "baz" in an
environment in which the only variable is "LOGNAME". Note that
the "-" option clears out the PATH variable, so one should be
careful to specify in which directory to find the program to
call.
env -u EDITOR LOGNAME=foo PATH=/energy -- e=mc2 bar baz
runs the program "/energy/e=mc2" with environment
{ LOGNAME=foo PATH=/energy }
*/
#include <stdio.h>
#include <getopt.h>
#include <sys/types.h>
#include "system.h"
int putenv ();
void error ();
static void usage ();
extern char **environ;
/* The name by which this program was run. */
char *program_name;
static struct option const longopts[] =
{
{"ignore-environment", no_argument, NULL, 'i'},
{"unset", required_argument, NULL, 'u'},
{NULL, 0, NULL, 0}
};
void
main (argc, argv, envp)
register int argc;
register char **argv;
char **envp;
{
char *dummy_environ[1];
int optc;
int ignore_environment = 0;
program_name = argv[0];
while ((optc = getopt_long (argc, argv, "+iu:", longopts, (int *) 0)) != EOF)
{
switch (optc)
{
case 'i':
ignore_environment = 1;
break;
case 'u':
break;
default:
usage ();
}
}
if (optind != argc && !strcmp (argv[optind], "-"))
ignore_environment = 1;
environ = dummy_environ;
environ[0] = NULL;
if (!ignore_environment)
for (; *envp; envp++)
putenv (*envp);
optind = 0; /* Force GNU getopt to re-initialize. */
while ((optc = getopt_long (argc, argv, "+iu:", longopts, (int *) 0)) != EOF)
if (optc == 'u')
putenv (optarg); /* Requires GNU putenv. */
if (optind != argc && !strcmp (argv[optind], "-"))
++optind;
while (optind < argc && index (argv[optind], '='))
putenv (argv[optind++]);
/* If no program is specified, print the environment and exit. */
if (optind == argc)
{
while (*environ)
puts (*environ++);
exit (0);
}
execvp (argv[optind], &argv[optind]);
error (errno == ENOENT ? 127 : 126, errno, "%s", argv[optind]);
}
static void
usage ()
{
fprintf (stderr, "\
Usage: %s [-] [-i] [-u name] [--ignore-environment] [--unset=name]\n\
[name=value]... [command [args...]]\n",
program_name);
exit (2);
}
|
