How do I use GetOptions to get the default argument?

Question

I've read the doc for GetOptions but I can't seem to find what I need... (maybe I am blind)

What I want to do is to parse command line like this

myperlscript.pl -mode [sth] [inputfile]

I can use the -mode part, but I am not sure how to get the [inputfile]. Any advice will be appreciated.

Answer 1

The command line arguments that don't begin with - will still be in @ARGV, won't they?

Answer 2

You don't use GetOptions for this task. GetOptions will simply parse options for you and leave everything that is not an option in @ARGV. So after calling GetOptions simply look at @ARGV for any file names passed on the command line.

Answer 3

Anything not handled by GetOptions is left in @ARGV. So you would likely want something like

use Getopt::Long;
my %opt
my $inputfile = 'default';
GetOptions(\%opt, 'mode=s');
$inputfile = $ARGV[0] if defined $ARGV[0];

Answer 4

GetOptions will leave any arguments that it didn't parse, in the @ARGV variable. So you can just loop over the @ARGV variable.

use Getopt::Long;
my %opt;
GetOptions(
  \%opt,
  'mode=s'
);

for my $filename (@ARGV){
  parse( $filename, \%opt );
}

There is another option, you can use the special <> argument callback option.

use Getopt::Long qw'permute';
our %opt;
GetOptions(
  \%opt,
  'mode=s',
  '<>' => sub{
    my($filename) = @_;
    parse( $filename, \%opt );
  }
);

This is useful if you want to be able to work on multiple files, but use different options for some of them.

perl test.pl -mode s file1 file2 -mode t file3

This example will set $opt{mode} to s, then it will call parse with file1 as an argument. Then it will call parse with file2 as the argument. It will then change $opt{mode} to t, and call parse with file3, as an argument.