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():
           _POSIX_C_SOURCE >= 200112L
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE

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  4.15  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
       https://www.kernel.org/doc/man-pages/.

GNU                                                2017-09-15                                          SETENV(3)