putenv - change or add an environment variable
#include <stdlib.h>
int putenv(char *string);Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
The putenv() function adds or changes the value of
environment variables. The argument string is of the form
name=value. If name does not already exist in
the environment, then string is added to the environment. If
name does exist, then the value of name in the
environment is changed to value. The string pointed to by
string becomes part of the environment, so altering the string
changes the environment.
The putenv() function returns zero on success. On
failure, it returns a nonzero value, and errno is set to
indicate the error.