NAME

       putenv - change or add an environment variable

SYNOPSIS

       #include <stdlib.h>

       int putenv(const char *string);

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 -1 if an error occurs.

ERRORS

       ENOMEM Insufficient space to allocate new environment.

NOTES

       The  putenv()  function is not required to be reentrant, and the one in libc4, libc5 and glibc2.0 is not,
       but the glibc2.1 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 automatic 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 glibc2.1.2.

       The BSD4.4 version, like glibc 2.0, uses a copy.

       SUSv2 removes the `const' from the prototype, and so does glibc 2.1.3.

CONFORMING TO

       SVID 3, POSIX, BSD 4.3

SEE ALSO

       getenv(3), setenv(3), unsetenv(3), environ(5)