SETENV(3)						     Linux Programmer's Manual							 SETENV(3)

NAME

       setenv - change or add an environment variable

SYNOPSIS

       #include <stdlib.h>

       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 nonzero; 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 suc-
       ceeds, and the environment is unchanged.

RETURN VALUE

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

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

ERRORS

       EINVAL name is NULL, points to a string of length 0, or contains an '=' character.

       ENOMEM Insufficient memory to add a new variable to the environment.

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 3.27 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
								    2009-09-20								 SETENV(3)