rem: if (fail)
add: if (read_utmp (filename, &n_users, &utmp_buf) != 0)
context: users (const char *filename){  int n_users;  STRUCT_UTMP *utmp_buf;  int fail = read_utmp (filename, &n_users, &utmp_buf);  if (fail)    error (EXIT_FAILURE, errno, "%s", filename);  list_entries_users (n_users, utmp_buf);}