I have a problem in interpreting the bytes from binary file in perl.
Snippet of the code :
open IMG_FH, $IMAGE_FILE or die $!;
binmode IMG_FH;
sysread(IMG_FH, $Var_Options, 2);
if ($Var_Options == 0)
{
print "Received 0\n";
}
elsif ($Var_Options == 28)
{
print "Received 0\n";
}
else
{
print "Error\n";
}
Even though I am sure that the word kept at the start of the binary file is : "001c" (Hexadecimal), I am ending up printing "Error";
Please help.
You're using the wrong tools if you're analyzing binary data.
Instead of doing a simple numeric equality test, you need to study pack, unpack, and the perlpacktut.
One very helpful tool is to use Data::Dump or the core library Data::Dumper.
I would rewrite your script to the following to inspect the first two bytes:
use strict;
use warnings;
use autodie;
my $file = 'test-all-the-things.jpg';
open my $fh, '<:raw', $file;
sysread $fh, my $data, 2;
use Data::Dump;
dd $data;
Outputs:
"\xFF\xD8"
This module adapts the output when one tries to analyze more than just 2 bytes:
sysread $fh, my $data, 20;
use Data::Dump;
dd $data;
Outputs:
pack("H*","ffd8ffe000104a46494600010101006000600000")
