SOLVED: Via the pseek function posted by BrowserUK:

use constant CHUNK => 4*1024;
sub pseek {
   my( $p, $o ) = @_;
   read( $p, my $discard, $CHUNK ), $o -= $CHUNK while $o > $CHUNK;
   read( $p, $discard, $o-1 );
   return $o;
}

[download]

Thanks to all for your help.

-------------------------------------

Short:

Is there a way to achieve seek()-type functionality on pipe output?

Long:

A project I'm working on reads files from a given offset. For bland text files, this is simple:

open(FILE, $path) || die "$!\n";
seek(FILE, $offset, 0);
while(<FILE>) {
    # do stuff
}
close FILE;

[download]

However, it also needs to be able to read compressed files. Rather than hardcoding each compression format handler, I'd like to just add a configuration directive that points my program at the appropriate cat tool for the format (zcat, bzcat, whatever happens to be relevant) and open it like this:

open(FILE, '-|', "$cat $file") || die "$!\n";

[download]

But as you all know, I can't seek() on a pipe.

How can I work around this? I could dump the output to a file and then read it back in, but this is horribly inefficient and will cause significant performance problems as the files can reach 300-500 MB.

Thanks for any help.

In reply to seek() functionality on pipes by HKS

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