#!/usr/bin/env perl

# URL: http://jenda.krynicky.cz/perl/GUIscripts.html
# code by: Jan Dubois <jand@ActiveState.com>

use strict;
unless (@ARGV == 2) {
    print "Usage: $0 exefile [CONSOLE|WINDOWS]\n";
    exit;
}
unless ($ARGV[1] =~ /^(console|windows)$/i) {
    print "Invalid subsystem $ARGV[1], please use CONSOLE or WINDOWS\n";
    exit;
}
my ($record,$magic,$offset,$size);
open EXE, "+< $ARGV[0]" or die "Cannot open $ARGV[0]: $!";
binmode EXE;
read EXE, $record, 32*4;
($magic,$offset) = unpack "Sx58L", $record;
die "Not an MSDOS executable file" unless $magic == 0x5a4d;
seek EXE, $offset, 0;
read EXE, $record, 24;
($magic,$size) = unpack "Lx16S", $record;
die "PE header not found" unless $magic == 0x4550;
die "Optional header not in NT32 format" unless $size == 224;
seek EXE, $offset+24+68, 0;
print EXE pack "S", uc($ARGV[1]) eq 'CONSOLE' ? 3 : 2;
close EXE;