]>
Commit | Line | Data |
---|---|---|
fea681da | 1 | .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
31cc8387 | 2 | .\" and Copyright (C) 2004, 2007 Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da | 3 | .\" |
93015253 | 4 | .\" %%%LICENSE_START(VERBATIM) |
fea681da MK |
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. | |
8 | .\" | |
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. | |
c13182ef | 13 | .\" |
fea681da MK |
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15 | .\" manual page may be incorrect or out-of-date.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 | |
20 | .\" professionally. | |
c13182ef | 21 | .\" |
fea681da MK |
22 | .\" Formatted or processed versions of this manual, if unaccompanied by |
23 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 24 | .\" %%%LICENSE_END |
fea681da MK |
25 | .\" |
26 | .\" References consulted: | |
27 | .\" Linux libc source code | |
28 | .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) | |
29 | .\" 386BSD man pages | |
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) | |
c11b1abf | 32 | .\" Modified 9 Jun 2004, Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da | 33 | .\" Changed unsetenv() prototype; added EINVAL error |
c8f2dd47 | 34 | .\" Noted nonstandard behavior of setenv() if name contains '=' |
279d6eea | 35 | .\" 2005-08-12, mtk, glibc 2.3.4 fixed the "name contains '='" bug |
fea681da | 36 | .\" |
4b8c67d9 | 37 | .TH SETENV 3 2017-09-15 "GNU" "Linux Programmer's Manual" |
fea681da MK |
38 | .SH NAME |
39 | setenv \- change or add an environment variable | |
40 | .SH SYNOPSIS | |
41 | .nf | |
42 | .B #include <stdlib.h> | |
68e4db0a | 43 | .PP |
fea681da | 44 | .BI "int setenv(const char *" name ", const char *" value ", int " overwrite ); |
68e4db0a | 45 | .PP |
fea681da MK |
46 | .BI "int unsetenv(const char *" name ); |
47 | .fi | |
68e4db0a | 48 | .PP |
cc4615cc MK |
49 | .in -4n |
50 | Feature Test Macro Requirements for glibc (see | |
51 | .BR feature_test_macros (7)): | |
52 | .in | |
68e4db0a | 53 | .PP |
cc4615cc MK |
54 | .ad l |
55 | .BR setenv (), | |
56 | .BR unsetenv (): | |
b671fb6c | 57 | .RS 4 |
2b1b0424 MK |
58 | _POSIX_C_SOURCE\ >=\ 200112L |
59 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE | |
b671fb6c | 60 | .RE |
cc4615cc | 61 | .ad b |
fea681da | 62 | .SH DESCRIPTION |
60a90ecd MK |
63 | The |
64 | .BR setenv () | |
c6fa0841 MK |
65 | function adds the variable |
66 | .I name | |
67 | to the | |
68 | environment with the value | |
69 | .IR value , | |
70 | if | |
71 | .I name | |
72 | does not | |
c13182ef | 73 | already exist. |
c6fa0841 MK |
74 | If |
75 | .I name | |
76 | does exist in the environment, then | |
77 | its value is changed to | |
51700fd7 | 78 | .IR value |
c6fa0841 MK |
79 | if |
80 | .I overwrite | |
81 | is nonzero; | |
82 | if | |
51700fd7 | 83 | .IR overwrite |
c6fa0841 MK |
84 | is zero, then the value of |
85 | .I name | |
779e42d0 MK |
86 | is not changed (and |
87 | .BR setenv () | |
88 | returns a success status). | |
f3268285 MK |
89 | This function makes copies of the strings pointed to by |
90 | .I name | |
91 | and | |
92 | .I value | |
93 | (by contrast with | |
94 | .BR putenv (3)). | |
fea681da | 95 | .PP |
60a90ecd MK |
96 | The |
97 | .BR unsetenv () | |
c6fa0841 MK |
98 | function deletes the variable |
99 | .I name | |
100 | from | |
fea681da | 101 | the environment. |
f3268285 MK |
102 | If |
103 | .I name | |
104 | does not exist in the environment, | |
105 | then the function succeeds, and the environment is unchanged. | |
47297adb | 106 | .SH RETURN VALUE |
60a90ecd MK |
107 | The |
108 | .BR setenv () | |
2a4b81ff MK |
109 | function returns zero on success, |
110 | or \-1 on error, with | |
111 | .I errno | |
112 | set to indicate the cause of the error. | |
847e0d88 | 113 | .PP |
60a90ecd MK |
114 | The |
115 | .BR unsetenv () | |
116 | function returns zero on success, | |
fea681da MK |
117 | or \-1 on error, with |
118 | .I errno | |
119 | set to indicate the cause of the error. | |
47297adb | 120 | .SH ERRORS |
fea681da MK |
121 | .TP |
122 | .B EINVAL | |
123 | .I name | |
2a4b81ff MK |
124 | is NULL, points to a string of length 0, |
125 | or contains an \(aq=\(aq character. | |
126 | .TP | |
127 | .B ENOMEM | |
128 | Insufficient memory to add a new variable to the environment. | |
6d682990 MS |
129 | .SH ATTRIBUTES |
130 | For an explanation of the terms used in this section, see | |
131 | .BR attributes (7). | |
74714ea8 | 132 | .ad l |
6d682990 MS |
133 | .TS |
134 | allbox; | |
135 | lb lb lb | |
136 | l l l. | |
137 | Interface Attribute Value | |
138 | T{ | |
139 | .BR setenv (), | |
140 | .BR unsetenv () | |
141 | T} Thread safety MT-Unsafe const:env | |
142 | .TE | |
74714ea8 | 143 | .ad |
47297adb | 144 | .SH CONFORMING TO |
246d0d44 | 145 | POSIX.1-2001, POSIX.1-2008, 4.3BSD. |
47297adb | 146 | .SH NOTES |
246d0d44 | 147 | POSIX.1 does not require |
f3268285 MK |
148 | .BR setenv () |
149 | or | |
150 | .BR unsetenv () | |
151 | to be reentrant. | |
847e0d88 | 152 | .PP |
60a90ecd MK |
153 | Prior to glibc 2.2.2, |
154 | .BR unsetenv () | |
155 | was prototyped | |
c6fa0841 MK |
156 | as returning |
157 | .IR void ; | |
158 | more recent glibc versions follow the | |
246d0d44 | 159 | POSIX.1-compliant prototype shown in the SYNOPSIS. |
fea681da | 160 | .SH BUGS |
246d0d44 | 161 | POSIX.1 specifies that if |
fea681da | 162 | .I name |
f81fb444 | 163 | contains an \(aq=\(aq character, then |
fea681da MK |
164 | .BR setenv () |
165 | should fail with the error | |
166 | .BR EINVAL ; | |
f81fb444 | 167 | however, versions of glibc before 2.3.4 allowed an \(aq=\(aq sign in |
fea681da | 168 | .IR name . |
47297adb | 169 | .SH SEE ALSO |
fea681da MK |
170 | .BR clearenv (3), |
171 | .BR getenv (3), | |
172 | .BR putenv (3), | |
aa949e2d | 173 | .BR environ (7) |