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 (and setenv() returns a success
       status).  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 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.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌─────────────────────┬───────────────┬─────────────────────┐
       │Interface            │ Attribute     │ Value               │
       ├─────────────────────┼───────────────┼─────────────────────┤
       │setenv(), unsetenv() │ Thread safety │ MT-Unsafe const:env │
       └─────────────────────┴───────────────┴─────────────────────┘

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, 4.3BSD.

NOTES

       POSIX.1 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-compliant prototype shown in the SYNOPSIS.

BUGS

       POSIX.1  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 4.04 of  the  Linux  man-pages  project.   A  description  of  the  project,
       information   about   reporting   bugs,   and   the  latest  version  of  this  page,  can  be  found  at
       http://www.kernel.org/doc/man-pages/.