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 con-
       trast 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 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 3.25 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)