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15 .\" manual page may be incorrect or out-of-date.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 2017-09-15 "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 _POSIX_C_SOURCE\ >=\ 200112L
59 || /* Glibc versions <= 2.19: */ _BSD_SOURCE
65 function adds the variable
68 environment with the value
76 does exist in the environment, then
77 its value is changed to
84 is zero, then the value of
88 returns a success status).
89 This function makes copies of the strings pointed to by
98 function deletes the variable
104 does not exist in the environment,
105 then the function succeeds, and the environment is unchanged.
109 function returns zero on success,
110 or \-1 on error, with
112 set to indicate the cause of the error.
116 function returns zero on success,
117 or \-1 on error, with
119 set to indicate the cause of the error.
124 is NULL, points to a string of length 0,
125 or contains an \(aq=\(aq character.
128 Insufficient memory to add a new variable to the environment.
130 For an explanation of the terms used in this section, see
137 Interface Attribute Value
141 T} Thread safety MT-Unsafe const:env
145 POSIX.1-2001, POSIX.1-2008, 4.3BSD.
147 POSIX.1 does not require
153 Prior to glibc 2.2.2,
158 more recent glibc versions follow the
159 POSIX.1-compliant prototype shown in the SYNOPSIS.
161 POSIX.1 specifies that if
163 contains an \(aq=\(aq character, then
165 should fail with the error
167 however, versions of glibc before 2.3.4 allowed an \(aq=\(aq sign in