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(): _XOPEN_SOURCE
	   || /* Glibc since 2.19: */ _DEFAULT_SOURCE
	   || /* Glibc versions <= 2.19: */ _SVID_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.  In the event of an error, errno is set to indicate the
       cause.

ERRORS

       ENOMEM Insufficient space to allocate new environment.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       +----------+---------------+---------------------+
       |Interface | Attribute	  | Value		|
       +----------+---------------+---------------------+
       |putenv()  | Thread safety | MT-Unsafe const:env |
       +----------+---------------+---------------------+
CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

NOTES

       The putenv() function is not required to be reentrant, and the one in glibc 2.0 is not, but the glibc 2.1 version is.

       Since version 2.1.2, the glibc implementation conforms 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  ver-
       sions  2.0  to  2.1.1  differ:  a copy of the string is used.  On the one hand this causes a memory leak, and on the other hand it violates
       SUSv2.

       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 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

GNU
								    2016-03-15								 PUTENV(3)