in reply to Re^9: How do I display only matches
in thread (SOLVED) How do I display only matches

Thank you for the RFC reference.
I believe that you are correct and that Perl's default text I/O layer will do what you say.
I currently don't have a UNIX system to test with, but yes, this is "the way it is supposed to work".

I someone is writing both ends of a client/server application, of course you can do whatever you want.You can even just send a binary packet.

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Re^11: How do I display only matches
by jcb (Parson) on Sep 28, 2019 at 04:32 UTC

    Note that on *nix, the "default text I/O layer" is probably effectively :raw and :crlf is not used unless requested, because the Unix convention is that text files store only <LF> at end-of-line and "\n" is <LF> in POSIX.

    And the reason that you are supposed to specifically say "\015\012" instead of "\r\n" is that the latter is the current platform's notion of "carriage return/line feed" and might not be the ASCII CR/ASCII LF that is supposed to be used on the network. (I seem to recall that classic MacOS interpreted "\r\n" as "\012\015" as one example. I suspect EBCDIC systems may be even more bizarre.)

    Edited 2019-10-01 by jcb: Clarify wording to address haukex's nitpick.

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      Note that on *nix, the "default text I/O layer" is probably :raw and :crlf is not used unless requested

      A bit of a nitpick, from PerlIO:

      :raw
      ... The implementation of :raw is as a pseudo-layer which when "pushed" pops itself and then any layers which do not declare themselves as suitable for binary data.

      The defaults on 5.28:

      $ perl -wMstrict -MData::Dump -e "dd PerlIO::get_layers(STDOUT)"
("unix", "perlio")

C:\>perl -wMstrict -MData::Dump -e "dd PerlIO::get_layers(STDOUT)"
("unix", "crlf")

      [download]

      Update: There appears to be a a bug in PerlIO::get_layers() that causes the :crlf layer to always be reported on Windows, even after a binmode. (But the PerlIO documentation does confirm the above defaults.)

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        The default on *nix is equivalent to using :raw, which also creates a portability issue since binmode is unnecessary for handling binary data on POSIX — it "just works" until someone runs the program on Windows and bytes start disappearing. :-)

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