IO::Select - OO interface to the select system call
use IO::Select;
$s = IO::Select->new();
$s->add(\*STDIN);
$s->add($some_handle);
@ready = $s->can_read($timeout);
@ready = IO::Select->new(@handles)->can_read(0);
The IO::Select package implements an object approach to the system select
function call. It allows the user to see what IO handles, see the IO::Handle manpage,
are ready for reading, writing or have an exception pending.
- new ( [ HANDLES ] )
-
The constructor creates a new object and optionally initialises it with a set
of handles.
- add ( HANDLES )
-
Add the list of handles to the
IO::Select object. It is these values that
will be returned when an event occurs. IO::Select keeps these values in a
cache which is indexed by the fileno of the handle, so if more than one
handle with the same fileno is specified then only the last one is cached.
Each handle can be an IO::Handle object, an integer or an array
reference where the first element is an IO::Handle or an integer.
- remove ( HANDLES )
-
Remove all the given handles from the object. This method also works
by the
fileno of the handles. So the exact handles that were added
need not be passed, just handles that have an equivalent fileno
- exists ( HANDLE )
-
Returns a true value (actually the handle itself) if it is present.
Returns undef otherwise.
- handles
-
Return an array of all registered handles.
- can_read ( [ TIMEOUT ] )
-
Return an array of handles that are ready for reading.
TIMEOUT is
the maximum amount of time to wait before returning an empty list, in
seconds, possibly fractional. If TIMEOUT is not given and any
handles are registered then the call will block.
- can_write ( [ TIMEOUT ] )
-
Same as
can_read except check for handles that can be written to.
- has_exception ( [ TIMEOUT ] )
-
Same as
can_read except check for handles that have an exception
condition, for example pending out-of-band data.
- count ()
-
Returns the number of handles that the object will check for when
one of the
can_ methods is called or the object is passed to
the select static method.
- bits()
-
Return the bit string suitable as argument to the core
select() call.
- select ( READ, WRITE, EXCEPTION [, TIMEOUT ] )
-
select is a static method, that is you call it with the package name
like new . READ , WRITE and EXCEPTION are either undef or
IO::Select objects. TIMEOUT is optional and has the same effect as
for the core select call.
The result will be an array of 3 elements, each a reference to an array
which will hold the handles that are ready for reading, writing and have
exceptions respectively. Upon error an empty list is returned.
Here is a short example which shows how IO::Select could be used
to write a server which communicates with several sockets while also
listening for more connections on a listen socket
use IO::Select;
use IO::Socket;
$lsn = IO::Socket::INET->new(Listen => 1, LocalPort => 8080);
$sel = IO::Select->new( $lsn );
while(@ready = $sel->can_read) {
foreach $fh (@ready) {
if($fh == $lsn) {
# Create a new socket
$new = $lsn->accept;
$sel->add($new);
}
else {
# Process socket
# Maybe we have finished with the socket
$sel->remove($fh);
$fh->close;
}
}
}
Graham Barr. Currently maintained by the Perl Porters. Please report all
bugs to <perlbug@perl.org>.
Copyright (c) 1997-8 Graham Barr <gbarr@pobox.com>. All rights reserved.
This program is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
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