I've never had a need to use seek() in my Perl years, so after I got looking at a piece of code BrowserUK posted earlier today, I thought I'd ask about it.

In the below code in the seek $fh, $_ *80, 0; line, I would believe that it would set the cursor to column 80 (times the multiple in the while(...)), but it then proceeds to print 78 chars to the file. When I look at the file, all lines start at column 0.

#! perl -slw
use strict;
use threads;

open my $fh, '>', 'junk.dat' or die $!;
$_->join for map {
    async {
        seek $fh, $_ *80, 0;
        print $fh $_ x 78;
    };
} 1 .. 4;
close $fh;

open $fh, '<', 'junk.dat' or die $!;
print while <$fh>;
close $fh;

[download]

perldoc -f seek doesn't help it click for me. Can someone advise what I'm missing in the above code? I did modify the code to try to understand, but the reason why things start at col 0 elude me.

-stevieb

In reply to Position in seek() confusion by stevieb

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