Penguin
Recent Changes
Annotated edit history of putenv(3) version 1, including all changes. View license author blame.
Rev Author # Line
1 perry 1 PUTENV
2 !!!PUTENV
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 RETURN VALUE
7 ERRORS
8 NOTES
9 CONFORMING TO
10 SEE ALSO
11 ----
12 !!NAME
13
14
15 putenv - change or add an environment variable
16 !!SYNOPSIS
17
18
19 __#include
20 __''string''__);
21 __
22 !!DESCRIPTION
23
24
25 The __putenv()__ function adds or changes the value of
26 environment variables. The argument ''string'' is of the
27 form ''name''=''value''. If ''name'' does not
28 already exist in the environment, then ''string'' is
29 added to the environment. If ''name'' does exist, then
30 the value of ''name'' in the environment is changed to
31 ''value''. The string pointed to by ''string'' becomes
32 part of the environment, so altering the string changes the
33 environment.
34 !!RETURN VALUE
35
36
37 The __putenv()__ function returns zero on success, or -1
38 if an error occurs.
39 !!ERRORS
40
41
42 __ENOMEM__
43
44
45 Insufficient space to allocate new environment.
46 !!NOTES
47
48
49 The __putenv()__ function is not required to be
50 reentrant, and the one in libc4, libc5 and glibc2.0 is not,
51 but the glibc2.1 version is.
52
53
54 Description for libc4, libc5, glibc: If the argument
55 ''string'' is of the form ''name'', and does not
56 contain an `=' character, then the variable ''name'' is
57 removed from the environment. If __putenv()__ has to
58 allocate a new array ''environ'', and the previous array
59 was also allocated by __putenv()__, then it will be
60 freed. In no case will the old storage associated to the
61 environment variable itself be freed.
62
63
64 The libc4 and libc5 and glibc 2.1.2 versions conform to
65 SUSv2: the pointer ''string'' given to __putenv()__ is
66 used. In particular, this string becomes part of the
67 environment; changing it later will change the environment.
68 (Thus, it is an error is to call __putenv()__ with an
69 automatic variable as the argument, then return from the
70 calling function while ''string'' is still part of the
71 environment.) However, glibc 2.0-2.1.1 differs: a copy of
72 the string is used. On the one hand this causes a memory
73 leak, and on the other hand it violates SUSv2. This has been
74 fixed in glibc2.1.2.
75
76
77 The BSD4.4 version, like glibc 2.0, uses a
78 copy.
79
80
81 SUSv2 removes the `const' from the prototype, and so does
82 glibc 2.1.3.
83 !!CONFORMING TO
84
85
86 SVID 3, POSIX, BSD 4.3
87 !!SEE ALSO
88
89
90 getenv(3), setenv(3), unsetenv(3),
91 environ(7)
92 ----
This page is a man page (or other imported legacy content). We are unable to automatically determine the license status of this page.