setenv - change or add an environment variable
#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)):
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.