Re^2: how to read binary file and give a binary output?

[mr_mischief]

This makes the assumption that the file fits in RAM. This is usually, but not always, a safe assumption. Things may get complicated if that's not the case. Since we're not talking about line-oriented text files read (and possibly sysread and syswrite) would be good additional reading.

If there are fixed-length records there are ways to deal with that. If there are record terminators consistent throughout the file, there's a way to deal with that, too. See $/ for more information.

[Loops]

Good point about it all having to fit into RAM. Should be relatively straightforward to read byte by byte, although looking ahead for the two byte separator would need some finagling. hmmm, how about:

my $ifilename = 'file.in';
my $ofilename = $ifilename . '.bin';

open my $ifile, '<', $ifilename or die "could not open input file $!";
open my $ofile, '>', $ofilename or die "could not open output file $!"
+;

binmode $ifile;
binmode $ofile;

my $n = eof($ifile) ? "" : getc($ifile);
while ((my $c = $n) ne "") {
        $n = eof($ifile) ? "" : getc($ifile);
        print $ofile "$c$n" eq "\x4F\xFF" .. 1 ? $c : "\x0";
}

close $ifile;
close $ofile;