Getopt::Long result issue

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

I have just begun using the Getopt::Long CPAN module, and I'm a bit confused about its return result. For example:

use strict;
use warnings;
use Getopt::Long;
{
    my $blah;
    my $result = GetOptions('blah=i'    =>  \$blah);

    print "result = $result\n";
    print "blah = $blah\n";
}
[download]

By my understanding, blah is a required integer value, but when i invoke my script without a blah arg, i still get a true result:

perl -w getopt_test.pl
result = 1
Use of uninitialized value in concatenation (.) or string at getopt_test.pl line 12.
blah =

It makes sense that $blah is uninitialized, but i thought that $result would be false.

When i invoke this with a blah option, i get a true result also:

perl -w getopt_test.pl --blah 4
result = 1
blah = 4

As a side note:
By my understanding, i dont need to say --blah=4, i can say --blah 4, and that seems to parse correctly by my test runs.

So what am i missing here?

Comment on Getopt::Long result issue Download Code

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Re: Getopt::Long result issue by Sidhekin (Priest) on Sep 07, 2004 at 16:03 UTC
By my understanding, blah is a required integer value, but when i invoke my script without a blah arg, i still get a true result What is "required" here is the integer value, not the parameter itself. That is, specifying blah without specifying a value will fail: `perl -w getopt_test.pl --blah Option blah requires an argument result = Use of uninitialized value in concatenation (.) or string at getopt_te +st.pl line 9. blah =` [download] Quoting from the documentation ... GetOptions does not return a false result when an option is not supplied That's why they're called 'options'. ... which says it all really ... :-) `print "Just another Perl ${\(trickster and hacker)},"` The Sidhekin proves Sidhe did it!	[reply] [d/l] [select]
Re: Getopt::Long result issue by Random_Walk (Prior) on Sep 07, 2004 at 16:07 UTC
When Getopt::Long says "requires a value" what it says is that if blah occurs it must have a value, not that blah is required. If you run your script with -blah (no value given) you will see $result is undef. I am afraid what you will have to do is check blah is set once you have eaten up the options. `use strict; use warnings; use Getopt::Long; { my $blah; my $result = GetOptions('blah=i' => \$blah); &usage unless $blah; print "result = $result\n"; print "blah = $blah\n"; } sub usage { print "$0: -blah=value\n" }` [download] Cheers, R.	[reply] [d/l]
Re: Getopt::Long result issue by herveus (Prior) on Sep 07, 2004 at 16:06 UTC
Howdy! Sidhekin covered the direct answer just fine. If you want to make 'blah' a mandatory option, just test $blah for definedness after the call to GetOptions, just as you would validate any other options for the right combinations or existence. yours, Michael	[reply]
Re: Getopt::Long result issue by Zaxo (Archbishop) on Sep 07, 2004 at 16:13 UTC
"Required" in the Getopt::Long docs means that a value is required, not that the option's use is required. If you want that, call `die 'Foo requires blah be specified' unless defined $blah;` after the GetOptions call. GetOptions returns undefined if options are misused or unknown options are given. After Compline, Zaxo	[reply]
Re: Getopt::Long result issue by perlfan (Parson) on Sep 07, 2004 at 18:15 UTC
If you want to test if something was passed, you need to test the reference that the options affects. `GetOptions` doesn't return anything of use. `#!/usr/bin/perl -w use strict; use Getopt::Long; my $fVal = 0; GetOptions( f => \$fVal, ) # if "-f" is used, this will print "1" else "0" print "$fVal\n";` [download]	[reply] [d/l] [select]