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.  In the event of an error, errno is set to indicate the
       cause.

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 3.53 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
								    2013-04-19								 PUTENV(3)