io::wrap(3)

NAME

IO::Wrap - wrap raw filehandles in IO::Handle interface

SYNOPSIS

use IO::Wrap;
### Do stuff with any kind of filehandle  (including  a
bare globref), or
###  any  kind  of  blessed  object  that responds to a
print() message.
###
sub do_stuff {
    my $fh = shift;
    ### At this point, we have no idea  what  the  user
gave us...
    ###  a  globref?  a FileHandle? a scalar filehandle
name?
    $fh = wraphandle($fh);
    ### At this point, we know we have  an  IO::Handlelike object!
    $fh->print("Hey there!");
    ...
}

DESCRIPTION

Let's say you want to write some code which does I/O, but
you don't want to force the caller to provide you with a
FileHandle or IO::Handle object. You want them to be able
to say:

do_stuff(TDOUT);
do_stuff('STDERR');
do_stuff($some_FileHandle_object);
do_stuff($some_IO_Handle_object);

And even:

do_stuff($any_object_with_a_print_method);

Sure, one way to do it is to force the caller to use
tiehandle(). But that puts the burden on them. Another way to do it is to use IO::Wrap, which provides you with the following functions:

wraphandle SCALAR

This function will take a single argument, and "wrap"
it based on what it seems to be...

· A raw scalar filehandle name, like "STDOUT" or

"Class::HANDLE". In this case, the filehandle
name is wrapped in an IO::Wrap object, which is
returned.

· A raw filehandle glob, like "TDOUT". In this

case, the filehandle glob is wrapped in an
IO::Wrap object, which is returned.

· A blessed FileHandle object. In this case, the

FileHandle is wrapped in an IO::Wrap object if and
only if your FileHandle class does not support the
"read()" method.

· Any other kind of blessed object, which is assumed

to be already conformant to the IO::Handle inter
face. In this case, you just get back that
object.

If you get back an IO::Wrap object, it will obey a basic
subset of the IO:: interface. That is, the following
methods (note: I said methods, not named operators) should work on the thing you get back:

close
getline
getlines
print ARGS...
read BUFFER,NBYTES
seek POS,WHENCE
tell

NOTES

Clearly, when wrapping a raw external filehandle (like
TDOUT), I didn't want to close the file descriptor when
the "wrapper" object is destroyed... since the user might
not appreciate that! Hence, there's no DESTROY method in
this class.

When wrapping a FileHandle object, however, I believe that
Perl will invoke the FileHandle::DESTROY when the last
reference goes away, so in that case, the filehandle is
closed if the wrapped FileHandle really was the last ref
erence to it.

WARNINGS

This module does not allow you to wrap filehandle names
which are given as strings that lack the package they were
opened in. That is, if a user opens FOO in package Foo,
they must pass it to you either as "OO" or as
"Foo::FOO". However, "STDIN" and friends will work just
fine.

VERSION

$Id: Wrap.pm,v 2.102 2001/08/17 02:06:33 eryq Exp $

AUTHOR

Eryq (eryq@zeegee.com). President, ZeeGee Software Inc (http://www.zeegee.com).

perl v5.8.0 2001-08-17 IO::Wrap(3)