NAME
    File::RandomLine - Retrieve random lines from a file

VERSION
    This documentation refers to version 0.19

SYNOPSIS
      # Fast but biased randomness
      use File::RandomLine;
      my $rl = File::RandomLine->new('/var/log/messages');
      print $rl->next;
      print join("\n",$rl->next(3));
  
      # Slow but uniform randomness
      $rl = File::RandomLine->new('/var/log/messages', {algorithm=>"uniform"});
  
DESCRIPTION
    This module provides a very fast random-access algorithm to retrieve
    random lines from a file. Lines are not retrieved with uniform
    probability, but instead are weighted by the number of characters in the
    previous line, due to the nature of the algorithm. Lines are most random
    when all lines are about the same length. For log file sampling or
    quote/fortune generation, this should be "random enough". Note -- when
    getting multiple lines, this module resamples with replacement, so
    duplicate lines are possible. Users will need to check for duplication
    on their own if this is not desired.

    The algorithm is as follows:

    *   Seek to a random location in the file

    *   Read and discard the line fragment found

    *   Read and return the next line, or the first line if we've reached
        the end of the file

    *   Repeat until the requested number of random lines have been found

    This module provides some similar behavior to File::Random, but the
    random access algorithm is much faster on large files. (E.g., it runs
    nearly instantaneously even on 100+ MB log files.)

    This module also provides an optional, slower algorithm that returns
    random lines with uniform probability.

USAGE
  "new"
     $rl = File::RandomLine->new( "filename" );
     $rl = File::RandomLine->new( "filename", { algorithm => "uniform" } );

    Returns a new File::RandomLine object for the given filename. The
    filename must refer to a readable file. A hash reference may be provided
    as an optional second argument to specify an algorithm to use. Currently
    supported algorithms are "fast" (the default) and "uniform". Under
    "uniform", the module indexes the entire file before selecting random
    lines with true uniform probability for each line. This can be
    significantly slower on large files.

  "next"
     $line = $rl->next();
     @lines = $rl->next(5);
     ($line1, $line2, $line3) = $rl->next();

    Returns one or more lines from the file. Without parameters, returns a
    single line if called in scalar context. With a positive integer
    parameter, returns a list with the specified number of lines. "next"
    also has some magic if called in list context with a finite length list
    of l-values and will return the proper number of lines.

INSTALLATION
    The following commands will build, test, and install this module:

     perl Build.PL
     perl Build
     perl Build test
     perl Build install

BUGS
    Please report bugs using the CPAN Request Tracker at
    http://rt.cpan.org/NoAuth/Bugs.html?Dist=File-RandomLine

AUTHOR
    David A Golden <dagolden@cpan.org>

    http://dagolden.com/

COPYRIGHT
    Concept and code for "magic" behavior in array context taken from
    File::Random by Janek Schleicher.

    All other code Copyright (c) 2005 by David A. Golden.

    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

    The full text of the license can be found in the LICENSE file included
    with this module.

SEE ALSO
    *   File::Random

    *   "Re^2: selecting N random lines from a file in one pass",
        perlmonks.org, static URL: http://perlmonks.thepen.com/417065.html