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    <p>What the "fastest, most efficient way" is might be a different question. This is a typical way to do something like that:</p> <pre><code>use strict; use warnings; local $/ = ","; my @file = &lt;DATA&gt;; say "Number of records: " . @file; my $half = int((@file/2)+0.5); say "Last half of records ($half):"; say @file[$half .. $#file]; __DATA__ 20121130092403000Server1::RedHat 1.2.3.4(1234),20121130092503000Server2::RedHat 5.6.7.8(1234),20121130092603000Server3::SUSE 9.8.7.6(9876),20121130092703000Server4::WindowsXP 5.6.7.8(6543), </code></pre> <p>Note that the DATA file handle is used for demonstration here. You can simply change <code>&lt;DATA&gt;</code> to <code>&lt;&gt;</code> to make it use file arguments instead.</p> <p>This will be somewhat less efficient because the file is read into memory, and that will consume memory, which can be costly for large files. An alternative is to simply run through the file and count the records, then reopen the file to do the printing. E.g.:</p> <pre><code>my $file = shift; local $/ = ","; open my $fh, "&lt;", $file or die $!; my $count; while (&lt;$fh&gt;) { $count++ } $count = int(($count/2)+0.5); open $fh, "&lt;", $file or die $!; while ($count-- &gt; 0) { &lt;$fh&gt; }; while (&lt;$fh&gt;) { print } </code></pre> <p>And of course these outputs need to be redirected, e.g. like so:</p> <pre><code>perl script.pl oldfile &gt; newfile </code></pre> <p>You may also like the <a href="http://search.cpan.org/perldoc?Tie%3a%3aFile" rel="nofollow"><code>Tie::File</code></a> module. E.g.:</p> <pre><code>use strict; use warnings; use Tie::File; my $file = shift; tie @array, 'Tie::File', $file or die $!; my $half = int((@array/2)+0.5); splice @array, 0, $half; untie @array; </code></pre> <p>Note that the effects of this is irreversible, so make backups before you try it. It is supposedly efficient even for large files, and does not read the file into memory.</p>
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    1. POUsing Perl, what's the best way to prune the first half of a file?
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    1. COThese files can get rather large, which is why I was looking for the most efficient way of pruning. If I schedule this new Perl script to run daily, then that'll keep the file size down somewhat. I'll start playing with this on a small file for starters.
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    2. COPerhaps you should look into something like a log rotation module instead. I believe *nix does that sort of thing automatically.
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