SETENV(3)		   Linux Programmers Manual		    SETENV(3)



NAME
       setenv - change or add an environment variable

SYNOPSIS
       #include 

       int setenv(const char *name, const char *value, int overwrite);

       int unsetenv(const char *name);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       setenv(), unsetenv(): _BSD_SOURCE || _POSIX_C_SOURCE >= 200112L ||
       _XOPEN_SOURCE >= 600

DESCRIPTION
       The setenv() function adds the variable name to	the  environment  with
       the value value, if name does not already exist.  If name does exist in
       the environment, then its value is changed to  value  if  overwrite  is
       non-zero;  if overwrite is zero, then the value of name is not changed.
       This function makes copies of the strings pointed to by name and  value
       (by contrast with putenv(3)).

       The unsetenv() function deletes the variable name from the environment.
       If name does not exist in the environment, then the function  succeeds,
       and the environment is unchanged.

RETURN VALUE
       The  setenv()  function	returns  zero  on  success, or -1 if there was
       insufficient space in the environment.

       The unsetenv() function returns zero on success, or -1 on  error,  with
       errno set to indicate the cause of the error.

ERRORS
       EINVAL name contained an '=' character.

CONFORMING TO
       4.3BSD, POSIX.1-2001.

NOTES
       POSIX.1-2001 does not require setenv() or unsetenv() to be reentrant.

       Prior to glibc 2.2.2, unsetenv() was prototyped as returning void; more
       recent glibc versions follow the POSIX.1-2001-compliant prototype shown
       in the SYNOPSIS.

BUGS
       POSIX.1-2001  specifies	that  if  name contains an '=' character, then
       setenv() should fail with the error EINVAL; however, versions of  glibc
       before 2.3.4 allowed an '=' sign in name.

SEE ALSO
       clearenv(3), getenv(3), putenv(3), environ(7)

COLOPHON
       This  page  is  part of release 3.05 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			     SETENV(3)