FAQ 5.39 How do I select a random line from a file?

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5.39: 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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