How can I print the lines in STDIN in random order in Perl?

Question

I want to do the inverse of sort(1) : randomize every line of stdin to stdout in Perl.

Answer 1

I bet real Perl hackers will tear this apart, but here it goes nonetheless.

use strict;
use warnings;
use List::Util 'shuffle';

my @lines = ();
my $bufsize = 512;
while() {
    push @lines, $_;
    if (@lines == $bufsize) {
        print shuffle(@lines);
        undef @lines;
    }
}
print shuffle(@lines);

Difference between this and the other solution:

• Will not consume all the input and then randomize it (memory hog), but will randomize every $bufsize lines (not truly random and slow as a dog compared to the other option).
• Uses a module which returns a new list instead of a in place editing Fisher - Yates implementation. They are interchangeable (except that you would have to separate the print from the shuffle). For more information type perldoc -q rand on your shell.