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Discussion started by: norsk hedensk
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IO::Wrap(3) User Contributed Perl Documentation 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::Handle-like object!
$fh->print("Hey there!");
...
}
DESCRIPTION
Let's say you want to write some code which does I/O, but you don't want to force the caller to provide you with a FileHandle or IO::Handle
object. You want them to be able to say:
do_stuff(*STDOUT);
do_stuff('STDERR');
do_stuff($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...
o 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.
o A raw filehandle glob, like "*STDOUT". In this case, the filehandle glob is wrapped in an IO::Wrap object, which is returned.
o 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.
o Any other kind of blessed object, which is assumed to be already conformant to the IO::Handle interface. 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 *STDOUT), 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 reference 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 "*FOO" or as "Foo::FOO". However, "STDIN" and friends will work just
fine.
VERSION
$Id: Wrap.pm,v 1.2 2005/02/10 21:21:53 dfs Exp $
AUTHOR
Primary Maintainer
David F. Skoll (dfs@roaringpenguin.com).
Original Author
Eryq (eryq@zeegee.com). President, ZeeGee Software Inc (http://www.zeegee.com).
POD ERRORS
Hey! The above document had some coding errors, which are explained below:
Around line 212:
'=item' outside of any '=over'
perl v5.16.2 2005-02-10 IO::Wrap(3)
