+ /* convert string to number */
+ err = strtol(argv[optind], NULL, 10);
+ /* testing error condition on conversion */
+ if (err==LONG_MIN) {
+ perror("Underflow on error code");
+ return 1;
+ } else if (err==LONG_MIN) {
+ perror("Overflow on error code");
+ return 1;
+ }
+ /* conversion is fine */