1 .\" Copyright (c) 1988, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" This code is derived from software contributed to Berkeley by
5 .\" the American National Standards Committee X3, on Information
6 .\" Processing Systems.
8 .\" Redistribution and use in source and binary forms, with or without
9 .\" modification, are permitted provided that the following conditions
11 .\" 1. Redistributions of source code must retain the above copyright
12 .\" notice, this list of conditions and the following disclaimer.
13 .\" 2. Redistributions in binary form must reproduce the above copyright
14 .\" notice, this list of conditions and the following disclaimer in the
15 .\" documentation and/or other materials provided with the distribution.
16 .\" 4. Neither the name of the University nor the names of its contributors
17 .\" may be used to endorse or promote products derived from this software
18 .\" without specific prior written permission.
20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 .\" @(#)getenv.3 8.2 (Berkeley) 12/11/93
43 .Nd environment variable functions
49 .Fn getenv "const char *name"
51 .Fn setenv "const char *name" "const char *value" "int overwrite"
53 .Fn putenv "char *string"
55 .Fn unsetenv "const char *name"
57 These functions set, unset and fetch environment variables from the
59 .Em environment list .
63 function obtains the current value of the environment variable,
65 The application should not modify the string pointed
72 function inserts or resets the environment variable
74 in the current environment list.
77 does not exist in the list,
78 it is inserted with the given
80 If the variable does exist, the argument
85 variable is not reset, otherwise it is reset
91 function takes an argument of the form ``name=value'' and
92 puts it directly into the current environment,
93 so altering the argument shall change the environment.
96 does not exist in the list,
97 it is inserted with the given
101 does exist, it is reset to the given
107 deletes all instances of the variable name pointed to by
111 If corruption (e.g., a name without a value) is detected while making a copy of
112 environ for internal usage, then
117 will output a warning to stderr about the issue, drop the corrupt entry and
118 complete the task without error.
122 function returns the value of the environment variable as a
127 is not in the current environment,
131 .Rv -std setenv putenv unsetenv
144 pointer, points to an empty string, or points to a string containing an
160 is the first character in
162 This does not follow the
171 failed because they were unable to allocate memory for the environment.
188 functions conforms to
207 and insert it into the environment using
209 This was changed to use
211 as the memory location of the ``name=value'' pair to follow the
217 that assign a larger-sized
219 than any previous value to the same
221 will result in a memory leak.
224 semantics for this function
225 (namely, that the contents of
227 are copied and that old values remain accessible indefinitely) make this
229 Future versions may eliminate one or both of these
230 semantic guarantees in order to fix the bug.