Convert a hex string in ASCII to the same hex values using Perl

Question

I have a hexadecimal value as an ASCII string in Perl:

42dc3f74212c4e74bab2 <-- This is a string, but this is also the actual hexadecimal value I need

I need to convert that to hex, and by converting I mean \\x42\\xdc\\x3f, etc.

$auth_key = pack("h*", $key); #It kind of works, but it gives me a low nibble, so I end up with 24 cd f3 , etc.

How can I convert this string into hexadecimal of the same values!

I'm trying to feed this into a UDP socket if that helps.

Answer 1

Use pack 'H*', $key .

From perldoc -fpack :

h  A hex string (low nybble first).
H  A hex string (high nybble first).

Here is some output from the shell:

$perl -E'print pack "H*","42dc3f74212c4e74bab2"' | hd
00000000  42 dc 3f 74 21 2c 4e 74  ba b2                    |B.?t!,Nt..|
0000000a

Answer 2

Another way:

use strict;
use warnings;
use 5.016;

my $str = "42dc3f74212c4e74bab2";
$str =~ s/(..)/chr(hex($1))/eg;  #hex() -> convert hex string to decimal number, chr() -> convert decimal number to a character(string).
say $str;

say (pack "H*","42dc3f74212c4e74bab2");

--output:--
B??t!,Nt??
B??t!,Nt??

Round trip with hexdump:

$ perl -E'print "42dc3f74212c4e74bab2" =~ s/(..)/chr(hex($1))/erg' | hexdump -C
00000000  42 dc 3f 74 21 2c 4e 74  ba b2                    |B.?t!,Nt..|
0000000a

pack()/unpack() are very efficient though, so they should be preferred.