Perl Programmers Reference Guide                          open(3)

NAME
     open - perl pragma to set default disciplines for input and
     output

SYNOPSIS
         use open IN => ":crlf", OUT => ":raw";

DESCRIPTION
     The open pragma is used to declare one or more default
     disciplines for I/O operations.  Any open() and readpipe()
     (aka qx//) operators found within the lexical scope of this
     pragma will use the declared defaults.  Neither open() with
     an explicit set of disciplines, nor sysopen() are influenced
     by this pragma.

     Only the two pseudo-disciplines ":raw" and ":crlf" are
     currently available.

     The ":raw" discipline corresponds to "binary mode" and the
     ":crlf" discipline corresponds to "text mode" on platforms
     that distinguish between the two modes when opening files
     (which is many DOS-like platforms, including Windows).
     These two disciplines are currently no-ops on platforms
     where binmode() is a no-op, but will be supported everywhere
     in future.

UNIMPLEMENTED FUNCTIONALITY
     Full-fledged support for I/O disciplines is currently
     unimplemented.  When they are eventually supported, this
     pragma will serve as one of the interfaces to declare
     default disciplines for all I/O.

     In future, any default disciplines declared by this pragma
     will be available by the special discipline name ":DEFAULT",
     and could be used within handle constructors that allow
     disciplines to be specified.  This would make it possible to
     stack new disciplines over the default ones.

         open FH, "<:para :DEFAULT", $file or die "can't open $file: $!";

     Socket and directory handles will also support disciplines
     in future.

     Full support for I/O disciplines will enable all of the
     supported disciplines to work on all platforms.

SEE ALSO
     the binmode entry in the perlfunc manpage, the open entry in
     the perlfunc manpage, the perlunicode manpage

2000-03-16          Last change: perl v5.6.0                    1