On Wed, Jun 25, 2003 at 12:49:01AM +0100, Ben Harris wrote:
> getopt(3) contains the following sample code for parsing -<number>
> options:

Well, there are two things I see.  Andrew pointed out what the probable
intent is.  First of all, note that this is listed in the "BUGS" section
of the man page...  :-)

Minor nits:
	'c' (or 'ch') should be declared.
	'c' and 'ch': "pick one and stick with it"

The bug looks to be that the second branch of the 'if' should probably read
something like:
		else {
			length = atoi(argv[optind - 1] + 1);
			optind++;
		}

> Can anyone explain what the second branch of the "if" is for, and how to
> trigger it?  For bonus points, explain how to add an extra option (say,
> "-a") in such a way that an argument of "-a0" doesn't cause a segfault
> there.

I suppose something like (untested):
	char *p;
	int ch;
	int length, aflag;

	length = 0; aflag = 0;
	while ((ch = getopt(argc, argv, "0123456789")) != -1) {
		switch (ch) {
		case 'a':
			aflag=1;
			break;
		case '0': case '1': case '2': case '3': case '4':
		case '5': case '6': case '7': case '8': case '9':
			p = argv[optind - 1];
			if (p[0] == '-' && p[1] == ch && !p[2])
				length = atoi(++p);
			else {
				length = atoi(argv[optind-1] + 1);
				optind++;
			}
			break;
		}
	}

This has the nasty side-effect of '-a15' and '-15a' meaning different
things.  Now how you fix this, I guess, depends on what semantics you're
looking for...

-allen

-- 
 Allen Briggs                     briggs@wasabisystems.com
 Wasabi Systems, Inc.             http://www.wasabisystems.com/