also, there is a subtle difference between the <> operator and the implementation showed in the original post (although not very useful I think).

consider this:

$ cat test1.pl
#!/usr/bin/perl

use strict;
use warnings;

while (<>){
  print;
}

$ cat > testfile
two
three

$ echo "one" | perl test1.pl testfile
one
two
three

$ cat test2.pl
#!/usr/bin/perl

use strict;
use warnings;

my $file = shift @ARGV;

my $ifh;
my $is_stdin = 0;
if (defined $file){
  open $ifh, "<", $file or die $!;
} else {
  $ifh = *STDIN;
  $is_stdin++;
}

while (<$ifh>){
   print
}
close $ifh unless $is_stdin;

$ echo "one" | perl test2.pl testfile
two
three

[download]

That is, the <> operator acts like: 

unshift(@ARGV, '-') unless @ARGV;
    while ($ARGV = shift) {
    open(ARGV, $ARGV);
    while (<ARGV>) {
        ...        # code for each line
    }
    }

[download]

i.e. processes STDIN AND any file given in the command line, while my implementation processes the file given in the command line OR STDIN.

citromatik

In reply to Re^2: input from STDIN or from a file by citromatik
in thread input from STDIN or from a file by citromatik

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