Perl：使用Getopt :: Long从命令行和[piped STDIN | file]中获取参数

Question

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,

Answer 1

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 = <>;