getopt(3) posting FLAME

[Peter da Silva]

Disclaimer: the following text should be ignored by 90% of the readers of
mod.std.c, since they've already gone through this.

> Second, it is very useful and should be used in all new programs.
> People should not write their own version of argument parsing
> in every new program, and get it wrong, when a standard argument
> parser is available.

Not when (as has been pointed out by many people) the standard argument parser
does the wrong thing. It can't even handle the arguments that sort(1) (V7)
uses, to wit:

	sort -mubdfincrtx

Where the final 'tx' means 'tab character <x>'. The rest of sort's arguments
are even less parsable by getopt. There is no reason for getopt's
insistence on lots of whitespace, nor for its ignoring argument order, nor
for its inability to handle '+' and '-' type command flags...

And finally it's too big. If your program takes the following arguments:

	foo [-someflags] [file]...

Which is the usual case, what's wrong with:

	char *prog;

	main(ac, av)
	int ac;
	char **av;
	{
		int flag = 0;

		prog = *av;
		while(av++, ac--)
			if(**av=='-')
				while(*++*av)
					switch(**av) {
						case 's': /* -s */
							sflag++;
							break;
						...
						case 'g': /* -g<s> */
							if(av[0][1])
								gchar = *++*av;
							else if(av[1])
								gchar = **++av;
							else
								usage(*av);
						default:
							usage(*av);
					}
			else {
				FILE *fp = fopen(*av, "r");
				if(fp) {
					do_something_with(fp, *av);
					fclose(fp);
				}
				flag = 1;
			}
		if(flag==0) /* no files processed */
			do_something_with(stdin, "standard input");
	}

which is not much more complex than the main you have to write with getopt to
do the same thing, allows more flexibility (foo -s -g:; foo -s -g :; foo -sg:;
foo -sg :), and produces a program that needs less core. If you think that's
a minor consideration, remember why vi doesn't use stdio on a PDP-11.