The simple combination of File::ReadBackwards, split join and reverse does it off disk, fast and efficiently. The split assumes some sort of space separated data but you could modify this if required. HTH 

C:\>type transpose.pl
#!/usr/bin/perl -w
use strict;
use File::ReadBackwards;
transpose( "c:/data.txt", "c:/data-transpose.txt" );

sub transpose {
    my ( $infile, $outfile ) = @_;
    tie *BW, 'File::ReadBackwards', $infile or die "Can't read $infile
+ $!\n";
    open OUT, ">$outfile" or die "Can't write $outfile $!\n";
    while( <BW> ) {
        chomp;
        print OUT join "\t", reverse(split ' '),"\n";
    }
    close BW;
    close OUT;
}


C:\>type data.txt
11      12      13
21      22      23
31      32      33

C:\>transpose.pl

C:\>type data-transpose.txt
33      32      31
23      22      21
13      12      11

C:\>

[download]

cheers

tachyon

In reply to Re: Binary file handling by tachyon
in thread Binary file handling by Hena

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