open(3) Perl Programmers Reference Guide open(3)NAMEopen - 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 every
where 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
2001-02-22 perl v5.6.1 open(3)
