1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\" and Copyright (C) 2004, 2007 Michael kerrisk <mtk.manpages@gmail.com>
4 .\" %%%LICENSE_START(VERBATIM)
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
26 .\" References consulted:
27 .\" Linux libc source code
28 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
30 .\" Modified Sat Jul 24 18:20:58 1993 by Rik Faith (faith@cs.unc.edu)
31 .\" Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aeb@cwi.nl)
32 .\" Modified 9 Jun 2004, Michael Kerrisk <mtk.manpages@gmail.com>
33 .\" Changed unsetenv() prototype; added EINVAL error
34 .\" Noted nonstandard behavior of setenv() if name contains '='
35 .\" 2005-08-12, mtk, glibc 2.3.4 fixed the "name contains '='" bug
37 .TH SETENV 3 2013-10-11 "GNU" "Linux Programmer's Manual"
39 setenv \- change or add an environment variable
42 .B #include <stdlib.h>
44 .BI "int setenv(const char *" name ", const char *" value ", int " overwrite );
46 .BI "int unsetenv(const char *" name );
50 Feature Test Macro Requirements for glibc (see
51 .BR feature_test_macros (7)):
58 _BSD_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600
64 function adds the variable
67 environment with the value
75 does exist in the environment, then
76 its value is changed to
83 is zero, then the value of
87 returns a success status).
88 This function makes copies of the strings pointed to by
97 function deletes the variable
103 does not exist in the environment,
104 then the function succeeds, and the environment is unchanged.
108 function returns zero on success,
109 or \-1 on error, with
111 set to indicate the cause of the error.
115 function returns zero on success,
116 or \-1 on error, with
118 set to indicate the cause of the error.
123 is NULL, points to a string of length 0,
124 or contains an \(aq=\(aq character.
127 Insufficient memory to add a new variable to the environment.
129 4.3BSD, POSIX.1-2001.
131 POSIX.1-2001 does not require
137 Prior to glibc 2.2.2,
142 more recent glibc versions follow the
143 POSIX.1-2001-compliant prototype shown in the SYNOPSIS.
145 POSIX.1-2001 specifies that if
147 contains an \(aq=\(aq character, then
149 should fail with the error
151 however, versions of glibc before 2.3.4 allowed an \(aq=\(aq sign in