Thanks for your advice !

It's interesting that binmode() only disables the :crlf layer but doesn't remove it. (Just discovered, that's actually documented in PerlIO.)

Does it still interfere with tell() even when it's disabled ? (perlport says: "If you use binmode on a file, however, you can usually seek and tell with arbitrary values in safety.")

I'm just curious, what happens if you try these on Windows:

open $fh, "<", $^X or die;
binmode $fh, ":raw";        # perldoc says: identical to 'binmode $fh'
print "3: ", join(' ', PerlIO::get_layers($fh, details => 1)), "\n";
close $fh;

open $fh, "<", $^X or die;
binmode $fh, ":raw:perlio"; # seems not useful (see below)
print "4: ", join(' ', PerlIO::get_layers($fh, details => 1)), "\n";
close $fh;

[download]

On UNIX that gives:

3: unix  4195328 perlio  4195328
4: unix  4195328 perlio  4195328 perlio  4195328

[download]

I know this discussion should probably go into a Perl develompent group but let me just explain where I'm having problems to understand things here:

If one has to use open($fh, '<:raw:perlio', $file) to get a clean and buffered binary stream this unconditionally forces a :perlio layer onto the stack, which in turn inserts a :unix layer below it.

Now, what about MacOS where Perl uses :stdio by default ? (I know far too little about MacOS but it must be faster than :unix:perlio there.) Also if someone wants to change the default layers via the PERLIO environment variable (for whatever reason), it would be blithely ignored on those streams.

In reply to Re^3: Using ":raw" layer in open() vs. calling binmode() by Anonymous Monk
in thread Using ":raw" layer in open() vs. calling binmode() by Anonymous Monk

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