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Date: Wed, 29 May 2002 15:33:19 -0700 (Pacific Daylight Time)
From: Michael A Chase <mchase AT ix DOT netcom DOT com>
Subject:  Re: trivial mkpasswd defect
To: Bernard A Badger <bab AT vx DOT com>, cygwin AT cygwin DOT com
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References:  <INEKLKBFCDBPKMKAJLMDGEJGCDAA DOT bab AT vx DOT com>
In-Reply-To:  <INEKLKBFCDBPKMKAJLMDGEJGCDAA.bab@vx.com>
Reply-To: Michael A Chase <mchase AT ix DOT netcom DOT com>
Message-Id: <E17DC0P-0006XD-00@blount.mail.mindspring.net>

On Wed, 29 May 2002 17:45:35 -0400 Bernard A Badger <bab AT vx DOT com> wrote:

> > -----Original Message-----
> > From: Michael A Chase [mailto:mchase AT ix DOT netcom DOT com]
> > To: Bernard A Badger; cygwin AT cygwin DOT com
> > Subject: Re: trivial mkpasswd defect
> > On Wed, 29 May 2002 12:27:15 -0400 Bernard A Badger <bab AT vx DOT com> wrote:
> >
> > > > -----Original Message-----
> > > > On Wed, May 29, 2002 at 10:14:14AM -0400, Jon LaBadie wrote:
> > > > > mkpasswd reports '?' is a valid help option but fails to accept
> it.
> > > > >         $ mkpasswd -?
> > > > >         mkpasswd: unknown option -- ?
> > > >
> > > > Thanks.  This will go away in the next version.
> > >
> > > I hope you mean that '-?' will work, not that '-?' will be taken out of the
> > > usage.
> >
> > In Unix envronments -h is more commonly used for help.  '-?' as an option
> > is subject to filename expansion which can lead to odd behavior if it isn't
> > quoted.

> Well, the example from man 2 getopt has this:
> 
>     while ((c = getopt(argc, argv, ":abf:o:")) != -1) {
>         switch(c) {
>         ....
>         case '?':
>                     fprintf(stderr,
>                             "Unrecognized option: -%c\n", optopt);
>             errflg++;
>         }
>     }
>     if (errflg) {
>         fprintf(stderr, "usage: . . . ");
>         exit(2);
> 
> Which exemplifies the custom of printing the "usage" upon an error.
> Since '?' cannot be used as a getopt option, it is guaranteed to cause
> getopt to return '?' no matter what the option characters are.
> 
> I saw this on a SGI Irix, and I checked at www.opengroup.org for the POSIX
> standard.
> 
> Of course, if you're not following POSIX, and aren't using getopt, it  may not
> work.  Your personal experience of '-h' being a "help" option, probably carries
> less weight than the endorsement of POSIX ;-)

I don't see anything there that says that POSIX endorses '-?' for
displaying the usage message.  It just shows how to handle invalid option
characters.  If getopt sees an invalid character after '-' it returns '?' and puts the
invalid character ("?" in your example) in optopt.  In that example, I'd expect to see

Unrecognized option -?
<<usage message>>

From 'man bash':

getopts optstring name [args]
       getopts is used by shell procedures to parse positional parameters.   optstring  contains  the
       option  characters  to  be  recognized;  if  a character is followed by a colon, the option is
       expected to have an argument, which should be separated from it by white space.  The colon and
       question  mark  characters  may  not  be  used as option characters. . . .

I don't have the man page for getopt() handy, but I think it contains the
same restriction.

-- 
Mac :})
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