Using the Perl rand() function

Introduction

The rand() function is used to generate random numbers. By default it generates a number between 0 and 1, however you can pass it a maximum and it will generate numbers between 0 and that number.

Example 1. Between 0 and 1

To generate a random decimal number between 0 and 1, use rand() without any parameters.

  #!/usr/bin/perl
  use strict;
  use warnings;

  my $random_number = rand();

  print $random_number . "\n";

This will give you a random number, like:

  0.521563085335405

Example 2. A bigger range of numbers

Quite often you don’t want a number between 0 and 1, but you want a bigger range of numbers. If you pass rand() a maximum, it will return a decimal number between 0 and that number. Our example below generates a random number between 0 and 100.

  #!/usr/bin/perl
  use strict;
  use warnings;

  my $range = 100;

  my $random_number = rand($range);

  print $random_number . "\n";

The program will produce something like:

  34.0500569277541

Example 3. A random integer

To generate a random integer, convert the output from rand to an integer, as follows:

  #!/usr/bin/perl
  use strict;
  use warnings;

  my $range = 100;

  my $random_number = int(rand($range));

  print $random_number . "\n";

This program gives you an integer from 0 to 99 inclusive:

  68

Example 4. With an offset

To generate a random number between, for example, 100 and 150, simply work out the range and add the minimum value to your random number.

  #!/usr/bin/perl
  use strict;
  use warnings;

  my $range = 50;
  my $minimum = 100;

  my $random_number = int(rand($range)) + $minimum;

  print $random_number . "\n";

This program gives you:

  129