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This is an excerpt from the latest version perlfaq5.pod, which
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5.38: How do I select a random line from a file?

Short of loading the file into a database or pre-indexing the lines in
the file, there are a couple of things that you can do.

Here's a reservoir-sampling algorithm from the Camel Book:

rand($.) < 1 && ($line = $_) while <>;

This has a significant advantage in space over reading the whole file
in. You can find a proof of this method in *The Art of Computer
Programming*, Volume 2, Section 3.4.2, by Donald E. Knuth.

You can use the "File::Random" module which provides a function for that

use File::Random qw/random_line/;
my $line = random_line($filename);

Another way is to use the "Tie::File" module, which treats the entire
file as an array. Simply access a random array element.


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