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

Hey Monks, I would like to write a subroutine to look for command-line arguments such as -help, -h, and --help. I wanna call my subrutine from a main program and the thing is: if I give the program any of the named command-line arguments, when you pass them into the subroutine it should return a true value. If this is the case, the program should print out a help message in a $USAGE variable and exit. My try is: 
#!/usr/bin/perl -w

$check = mycheck($#ARGV);

if ($check != 1) {
    $usage = "Help arguments have been found";
    print $usage, "\n";
}


sub mycheck {
my($#ARGV) = @_; 
    $return = 0; #Variable RETURN set as false (set as 0)
    foreach $arg (0 .. $#ARGV) {
        if (($arg eq '-help') || ($arg eq '-h') || ($arg eq '--help'))
+ {
        $return = 1; #Variable return now is true
        exit;
        } else {
        print "No help arguments found\n";
        }
    }
return $return
}

[download]
But it looks like not working and I cannot find the reason. Any ideas? when I run it it returns "syntax error at ex4HW01.pl line 13, near "0;" THANKS!

Replies are listed 'Best First'.
Re: ARGV issue
by ikegami (Patriarch) on Oct 02, 2011 at 21:57 UTC

    You have a couple mistakes.

    • my($#ARGV) = @_; makes no sense.

    • $arg contains a number, so it'll never be equal to any of the strings to which you compare it. You would need to loop over @ARGV.

    I'd use Getopt::Long. 

    use Getopt::Long qw( GetOptions );

sub usage {
   print STDERR "...simple usage...\n";
   exit(1);
}

sub help {
   print "...more extensive help...\n";
   exit(0);
}

GetOptions(
   'h|?|help' => \&help,
   ...
)
   or usage();

    [download]

    You might also find Pod::Usage of interest.

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Re: ARGV issue
by TomDLux (Vicar) on Oct 03, 2011 at 02:39 UTC

    I use Getopts:;Long to parse command line arguments, and Pod::usage to display the POD documentation which is in the same file.

    use POSIX qw{strftime};
use Getop:;Long;
use Pod::Usage;

my %options = (date => strftime( %Y-%m-%d);

Getopts( \%options, 'date=s', 'help', 'man' )
   or pod2usage( { '-message' => 'Error processing command line args',
+ 
                   '-verbose' => 0,
                   '-exitval' => 1,
                           });
pod2usage( { '-verbose' => 1 }) if exists $options{help};
pod2usage( { '-verbose' => 2 }) if exists $options{man};
__END__
=head1 NAME

myprog - Use it to demo Getopt::Long and Pod::Usage

=head1 SYNOPSIS

 myprog [-date yyyy-mm-dd] [-help] --man'

=head1 ARGUMENTS

=over 4

=item -date yyyy-mm-dd

The date to process. If not specified, today's date is used.

=item -help

Display a brief summary of the documentation, but not as brief
as shown for a command line argument error.

=item -man

Display complete man page.

=back

=head1 DESCRIPTION

This is what the program does, and how it works.

=head1 AUTHOR


me

=cut

    [download]

    As Occam said: Entia non sunt multiplicanda praeter necessitatem.

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Re: ARGV issue
by jwkrahn (Abbot) on Oct 02, 2011 at 22:24 UTC

    Try it like this: 

    #!/usr/bin/perl
use warnings;
use strict;

if ( grep /^(?:--help|-help|-h)$/, @ARGV ) {
    print "Help arguments have been found\n";
}
else {
    print "No help arguments found\n";
}

    [download]
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Re: ARGV issue
by dwm042 (Priest) on Oct 03, 2011 at 17:56 UTC
[reply]

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