GetOptions and help

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

What am I doing wrong in this code ?
I'm trying to allow the help usage to be printed if either no command line options are used or if the -h is used.

Use Getopt::Long;

Getopt::Long::Configure ("bundling");

if (!GetOptions(
            'U:s'      => \$upd,
            'mod'      => \$mod,
            'res'      => \$res,
            'h'        => \$help
   )) {
    usage();
    exit(1);
   }

if ($help) {
    usage();
    exit(1);
}
[download]

It works if I use

prog.pl -h
[download]

But not if I just type

prog.pl
[download]

I was expecting the help to be printed in this case also ?

Comment on GetOptions and help Select or Download Code

Replies are listed 'Best First'.
Re: GetOptions and help by wazoox (Prior) on Mar 16, 2006 at 12:11 UTC
It'ds clearly written into Getopt::Long documentation: `Trouble Shooting GetOptions does not return a false result when an option is not + sup- plied That's why they're called 'options'.` [download] So if you want to make some option mandatory, you'll have to check it by yourself : `usage() unless $res;` [download]	[reply] [d/l] [select]
Re^2: GetOptions and help by Anonymous Monk on Mar 16, 2006 at 12:31 UTC
None of the options are mandatory and I don't want them to be. Hence the question still remains . Unless you are suggesting that I have to check for each arguments existence e.g. `usage() unless $res or $mod or $upd` [download] This seems an untidy way to do it ?	[reply] [d/l]
Re^3: GetOptions and help by fishbot_v2 (Chaplain) on Mar 16, 2006 at 12:59 UTC
If none of the options are mandatory, why would you print usage in the second case?	[reply]
Re^4: GetOptions and help by chargrill (Parson) on Mar 16, 2006 at 13:15 UTC
Re^4: GetOptions and help by Anonymous Monk on Mar 16, 2006 at 13:26 UTC
Re: GetOptions and help by pboin (Deacon) on Mar 16, 2006 at 12:48 UTC
Try just testing the number of incoming parms, which is in @ARGV.. `if ( @ARGV == 0 \|\| $help ) { usage(); exit(1); }` [download]	[reply] [d/l]
Re^2: GetOptions and help by Anonymous Monk on Mar 16, 2006 at 13:01 UTC
I had previously tried doing this but it seems that in my case @ARGV is always -1 regardless of the number of arguments. Hence if I do this `$numargs = $#ARGV +1; if ($numargs == 0) { usage(); exit(1) }` [download] The usage always kicks in regardless of any options that may have been used	[reply] [d/l]
Re^3: GetOptions and help by fishbot_v2 (Chaplain) on Mar 16, 2006 at 16:38 UTC
`GetOptions` is destructive: it consumes `@ARGV` as it processes. You would need to test `@ARGV` before calling `GetOptions`. I would suggest this instead, though: Just determine what the required arguments are, and test them. In your case, it seems like the required arguments are an alternation: `unless ( $alt1 or $alt2 or ( $alt3 and $alt4 )) { usage(); exit; }` [download]	[reply] [d/l] [select]