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(<STDIN>) {     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.