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1 | .\" Copyright (c) 1988, 1991, 1993 | ||
2 | .\" The Regents of the University of California. All rights reserved. | ||
3 | .\" | ||
4 | .\" This code is derived from software contributed to Berkeley by | ||
5 | .\" the American National Standards Committee X3, on Information | ||
6 | .\" Processing Systems. | ||
7 | .\" | ||
8 | .\" Redistribution and use in source and binary forms, with or without | ||
9 | .\" modification, are permitted provided that the following conditions | ||
10 | .\" are met: | ||
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 | .\" 3. 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. | ||
19 | .\" | ||
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 | ||
30 | .\" SUCH DAMAGE. | ||
31 | .\" | ||
32 | .\" $OpenBSD: getenv.3,v 1.8 2003/06/02 20:18:37 millert Exp $ | ||
33 | .\" | ||
34 | .Dd December 11, 1993 | ||
35 | .Dt GETENV 3 | ||
36 | .Os | ||
37 | .Sh NAME | ||
38 | .Nm getenv , | ||
39 | .Nm putenv , | ||
40 | .Nm setenv , | ||
41 | .Nm unsetenv | ||
42 | .Nd environment variable functions | ||
43 | .Sh SYNOPSIS | ||
44 | .Fd #include <stdlib.h> | ||
45 | .Ft char * | ||
46 | .Fn getenv "const char *name" | ||
47 | .Ft int | ||
48 | .Fn setenv "const char *name" "const char *value" "int overwrite" | ||
49 | .Ft int | ||
50 | .Fn putenv "const char *string" | ||
51 | .Ft void | ||
52 | .Fn unsetenv "const char *name" | ||
53 | .Sh DESCRIPTION | ||
54 | These functions set, unset, and fetch environment variables from the host | ||
55 | .Em environment list . | ||
56 | For compatibility with differing environment conventions, the given arguments | ||
57 | .Fa name | ||
58 | and | ||
59 | .Fa value | ||
60 | may be appended and prepended, respectively, with an equal sign | ||
61 | .Dq Li \&= . | ||
62 | .Pp | ||
63 | The | ||
64 | .Fn getenv | ||
65 | function obtains the current value of the environment variable, | ||
66 | .Fa name . | ||
67 | If the variable | ||
68 | .Fa name | ||
69 | is not in the current environment, a null pointer is returned. | ||
70 | .Pp | ||
71 | The | ||
72 | .Fn setenv | ||
73 | function inserts or resets the environment variable | ||
74 | .Fa name | ||
75 | in the current environment list. | ||
76 | If the variable | ||
77 | .Fa name | ||
78 | does not exist in the list, it is inserted with the given | ||
79 | .Fa value . | ||
80 | If the variable does exist, the argument | ||
81 | .Fa overwrite | ||
82 | is tested; if | ||
83 | .Fa overwrite | ||
84 | is zero, the variable is not reset, otherwise it is reset to the given | ||
85 | .Fa value . | ||
86 | .Pp | ||
87 | The | ||
88 | .Fn putenv | ||
89 | function takes an argument of the form | ||
90 | .Ar name Ns No = Ns Ar value | ||
91 | and is equivalent to: | ||
92 | .Bd -literal -offset indent | ||
93 | setenv(name, value, 1); | ||
94 | .Ed | ||
95 | .Pp | ||
96 | The | ||
97 | .Fn unsetenv | ||
98 | function deletes all instances of the variable name pointed to by | ||
99 | .Fa name | ||
100 | from the list. | ||
101 | .Sh RETURN VALUES | ||
102 | The functions | ||
103 | .Fn setenv | ||
104 | and | ||
105 | .Fn putenv | ||
106 | return zero if successful; otherwise the global variable | ||
107 | .Va errno | ||
108 | is set to indicate the error and \-1 is returned. | ||
109 | .Pp | ||
110 | If | ||
111 | .Fn getenv | ||
112 | is successful, the string returned should be considered read-only. | ||
113 | .Sh ERRORS | ||
114 | .Bl -tag -width [ENOMEM] | ||
115 | .It Bq Er ENOMEM | ||
116 | The function | ||
117 | .Fn setenv | ||
118 | or | ||
119 | .Fn putenv | ||
120 | failed because they were unable to allocate memory for the environment. | ||
121 | .El | ||
122 | .Sh SEE ALSO | ||
123 | .Xr csh 1 , | ||
124 | .Xr sh 1 , | ||
125 | .Xr execve 2 , | ||
126 | .Xr environ 7 | ||
127 | .Sh STANDARDS | ||
128 | The | ||
129 | .Fn getenv | ||
130 | function conforms to | ||
131 | .St -ansiC . | ||
132 | .Sh HISTORY | ||
133 | The functions | ||
134 | .Fn setenv | ||
135 | and | ||
136 | .Fn unsetenv | ||
137 | appeared in | ||
138 | .At v7 . | ||
139 | The | ||
140 | .Fn putenv | ||
141 | function appeared in | ||
142 | .Bx 4.3 Reno . | ||