#!/usr/bin/env perl
  
  # Copyright 2013  Johns Hopkins University (author: Daniel Povey)
  
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #  http://www.apache.org/licenses/LICENSE-2.0
  #
  # THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  # KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
  # WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
  # MERCHANTABLITY OR NON-INFRINGEMENT.
  # See the Apache 2 License for the specific language governing permissions and
  # limitations under the License.
  
  
  if ($ARGV[0] eq "--srand") {
    $n = $ARGV[1];
    $n =~ m/\d+/ || die "Bad argument to --srand option: \"$n\"";
    srand($ARGV[1]);
    shift;
    shift;
  } else {
    srand(0); # Gives inconsistent behavior if we don't seed.
  }
  
  if (@ARGV > 1 || $ARGV[0] =~ m/^-.+/) { # >1 args, or an option we 
    # don't understand.
    print "Usage: shuffle_list.pl [--srand N] [input file]  > output
  ";
    print "randomizes the order of lines of input.
  ";
    exit(1);
  }
  
  @lines;
  while (<>) {
    push @lines, [ (rand(), $_)] ;
  }
  
  @lines = sort { $a->[0] cmp $b->[0] } @lines;
  foreach $l (@lines) {
      print $l->[1];
  }