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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.

       The unsetenv() function deletes the variable name from the environment.

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

       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

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