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Hex dump

by kschwab (Vicar)
on Sep 10, 2001 at 19:08 UTC ( #111481=snippet: print w/replies, xml ) Need Help??
Description: subroutine to print a hexdump of a string. I saw some discussion in the CB about needing such a thing.

Update: Also see HexView by OeufMayo.

sub hdump {
    my $offset = 0;
    foreach my $data (unpack("a16"x(length($_[0])/16)."a*",$_[0])) {
        if ($len == 16) {
            @array = unpack('N4', $data);
            $format="0x%08x (%05d)   %08x %08x %08x %08x   %s\n";
        } else {
            @array = unpack('C*', $data);
            $_ = sprintf "%2.2x", $_ for @array;
            push(@array, '  ') while $len++ < 16;
            $format="0x%08x (%05d)" .
               "   %s%s%s%s %s%s%s%s %s%s%s%s %s%s%s%s   %s\n";
        $data =~ tr/\0-\37\177-\377/./;
        printf $format,$offset,$offset,@array,$data;
        $offset += 16;
Update: Fixed the map() in a void context problem. Thanks merlyn. For the curious, it sort of evolved into a void context as I cleaned up the subroutine before posting it to perlmonks.
Replies are listed 'Best First'.
Re: Hex dump
by merlyn (Sage) on Sep 11, 2001 at 02:01 UTC
    I really dislike the "void map" there, for things like:
    map {$_ = sprintf('%2.2x',$_)} @array;
    What's wrong with simply:
    $_ = sprintf "%2.2x", $_ for @array;
    It even comes in at fewer characters, as well as running faster!

    -- Randal L. Schwartz, Perl hacker

Re: Hex dump
by tokai (Initiate) on Aug 29, 2015 at 00:06 UTC

    I liked the output of this function, so I used it for debugging purposes for a while... but in the end I wrote my own simplified variant with some other ideas from here and there which produces exactly the same output:

    sub hexdump($) { my $offset = 0; foreach my $chunk (unpack "(a16)*", $_[0]) { my $hex = unpack "H*", $chunk; # hexadecimal magic $chunk =~ tr/ -~/./c; # replace unprintables $hex =~ s/(.{1,8})/$1 /gs; # insert spaces printf "0x%08x (%05u) %-*s %s\n", $offset, $offset, 36, $hex, $chunk; $offset += 16; } }
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