Perl: Take arguments from both command line and [piped STDIN|file], using Getopt::Long

1
votes

Hi I wanted to implement both command line argument1, and either piped STDIN (through lone single dash '-') or a filename as argument2, using Getop::Long in Perl. In perldoc it is merely mentioned a little bit "A lone dash on the command line will now be a legal option, and using it will set variable $stdio": (https://perldoc.perl.org/Getopt/Long.html). But this is far from what I can use. I tried the following

#!/usr/bin/perl -w
use strict;
use Getopt::Long;
my ($se, $st);
GetOptions("se=s" => \$s, '' => \$st) or die "Usage: $0 -s <tab|space|comma>\n";
$st = <STDIN>;
print "$se\n$st\n";

However $st only returns the first line or should I use a filehandle? Then what if the lone single dash '-' is not there and a filename is specified as argument2? Thanks a lot,

1
perlstdingetopt-long
Can you show examples of usage you need? When you set up an option --o (for example) with Getopt, both script.pl -o val file and echo "..." | script.pl -o val will read in the option value and you'll be able to read either from the pipe or the file with while (<>). (Is that not what you want?) - zdim
@zdim It is something like script.pl -s tab filename or head -3 filename | script.pl -s tab - - Yiran Guo
Then that should work exactly as in my comment (see @ikegami answer). Note that you do not need the - for what you want. - zdim
Aha yes thanks a lot @zdim - Yiran Guo

1 Answers

2
votes

Just use <> (short for <ARGV>) instead of <STDIN>. ARGV is a special handle that reads from STDIN if @ARGV is empty, and reads from the each of the files specified in @ARGV if it's not.

GetOptions("se=s" => \my $se)
   or die "Usage: $0 -s <tab|space|comma>\n";

my $st = <>;