char *catgets(nl_catd catd, int set_num, int msg_num, const char *s);
catgets() attempts to read message msg_num, in set set_num, from the message catalog identified by catd. catd is a catalog descriptor returned from an earlier call to catopen(). s points to a default message string which will be returned by catgets() if the identified message catalog is not currently available.
If the identified message is retrieved successfully, catgets() returns a pointer to an internal buffer area containing the null terminated message string. If the call is unsuccessful for any reason, catgets() returns a pointer to s.