[vox-tech] writing free getopt, ran into a dilemma...

[Mark K. Kim]

Keywords: getopt, license issues, GPL, BSD, optind

Hey guys,

I mentioned some months ago about how I was using GPL's "getopt" library
in one of my company programs, and I was wondering about the GPL
distribution issues.[1]

Anyway, now I'm writing a software I want to release with BSD license,
but I also want the GNU getopt statically-linked.  Since I can't do that,
I decided to write my own GNU-compatible getopt library.  I know Micah
offered to do this if I wanted it badly enough, but I thought it'd be an
interesting challenge so I decided to try it myself.

The library is interestingly working really well.  I wrote a test program,
and I can't tell the difference between the GNU version and mine! :)  But
I've ran into a dilemma regarding how the library should behave, and I
thought I should get some feedback from this group of geniuses :)

The getopt library has the following parts:

   char* optarg; (the argument to an option)
   int optind;   (argv[optind] will be processed at next getopt() call)
   int opterr;   (if true, getopt() will print error on invalid option)
   int optopt;   (getopt() returns this on invalid option)

   int getopt(int argc, const char* argv[], const char* optstr);
                 (the actual getopt() call)

I implemented everything.  optarg, opterr, and optopt work exactly
identical to GNU's getopt.  However, optind is a little different because
my library doesn't reshuffle argv[] like GNU's getopt.  That's okay with
me, but things get hairy if "optstr" doesn't have '-' as its first
character -- then the programmer is expected to search the remaining
argv[] starting with "optind"... but due to GNU getopt's flexible nature,
there could be unhandled entries in argv[] not only at the end but in the
middle, too (creating "holes" of unhandled optarg in argv[]).  So where
should "optind" point to by the time "getopt"  finishes processing all the
options and there are "holes" of unhandled optarg only plain strings
remain?  (That's a little long and confusing; I hope you understand all
that :)

I think I now understand why GNU shuffles argv[].  But I don't need this
to be fully compatible with BSD's getopt; I just need it to behave in
reasonable manner.  I'd like to hear some ideas and what you think the
behavior should be and how it's better than others.

Thanks!

-Mark

[1] - Interesting how that issue came up on Slashdot a couple days ago,
and the answers were pretty much what I got here :)

--
Mark K. Kim
http://www.cbreak.org/
PGP key available upon request.