get environment variables from /etc/environment
const char *pam_getenv(pam_handle_t *pamh, const char *name);
The pam_getenv function searches the PAM environment list as associated with the handle pamh for an item that matches the string pointed to by name and returns a pointer to the value of the environment variable. The application is not allowed to free the data.
The pam_getenv function returns NULL on failure.
pam_start(3), pam_getenvlist(3), pam_putenv(3), pam(8)