putenv(3C)putenv(3C)NAME
putenv() - change or add value to environment
SYNOPSIS DESCRIPTION
string points to a string of the form name=value. makes the value of the environment variable name equal to value by altering an existing
variable or creating a new one. In either case, the string pointed to by string becomes part of the environment, so altering the string
changes the environment. The space used by string is no longer used once a new string-defining name is passed to
EXTERNAL INFLUENCES
Locale
The category determines the interpretation of characters in string as single- and/or multi-byte characters.
International Code Set Support
Single- and multi-byte character code sets are supported.
DIAGNOSTICS
returns non-zero if it was unable to obtain enough space via for an expanded environment, or if an invalid multibyte character sequence was
encountered in the string argument; otherwise it returns zero.
ERRORS
fails under the following conditions:
[ENOMEM] There is insufficient space to expand the environment.
[EILSEQ] An invalid multibyte character sequence was encountered in the string argument.
WARNINGS
manipulates the environment pointed to by environ, and can be used in conjunction with However, envp (the third argument to main) is not
changed.
This routine uses to enlarge the environment (see malloc(3C)).
After is called, environmental variables are not in alphabetical order.
A potential error is to call with an automatic variable as the argument, then exit the calling function while string is still part of the
environment.
SEE ALSO exec(2), getenv(3C), malloc(3C), environ(5), thread_safety(5).
STANDARDS CONFORMANCE putenv(3C)
Check Out this Related Man Page
PUTENV(3) Linux Programmer's Manual PUTENV(3)NAME
putenv - change or add an environment variable
SYNOPSIS
#include <stdlib.h>
int putenv(char *string);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
putenv(): _SVID_SOURCE || _XOPEN_SOURCE
DESCRIPTION
The putenv() function adds or changes the value of environment variables. The argument string is of the form name=value. If name does not
already exist in the environment, then string is added to the environment. If name does exist, then the value of name in the environment
is changed to value. The string pointed to by string becomes part of the environment, so altering the string changes the environment.
RETURN VALUE
The putenv() function returns zero on success, or nonzero if an error occurs.
ERRORS
ENOMEM Insufficient space to allocate new environment.
CONFORMING TO
SVr4, POSIX.1-2001, 4.3BSD.
NOTES
The putenv() function is not required to be reentrant, and the one in libc4, libc5 and glibc 2.0 is not, but the glibc 2.1 version is.
Description for libc4, libc5, glibc: If the argument string is of the form name, and does not contain an '=' character, then the variable
name is removed from the environment. If putenv() has to allocate a new array environ, and the previous array was also allocated by
putenv(), then it will be freed. In no case will the old storage associated to the environment variable itself be freed.
The libc4 and libc5 and glibc 2.1.2 versions conform to SUSv2: the pointer string given to putenv() is used. In particular, this string
becomes part of the environment; changing it later will change the environment. (Thus, it is an error is to call putenv() with an auto-
matic variable as the argument, then return from the calling function while string is still part of the environment.) However, glibc
2.0-2.1.1 differs: a copy of the string is used. On the one hand this causes a memory leak, and on the other hand it violates SUSv2. This
has been fixed in glibc 2.1.2.
The 4.4BSD version, like glibc 2.0, uses a copy.
SUSv2 removes the const from the prototype, and so does glibc 2.1.3.
SEE ALSO clearenv(3), getenv(3), setenv(3), unsetenv(3), environ(7)COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2007-07-26 PUTENV(3)