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)->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 Handle, are ready for reading, writing or have an error condition pending.
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 a IO::Handle
or an integer.
TIMEOUT
is the maximum amount of time to wait before returning an empty list. If
TIMEOUT
is not given and any handles are registered then the call will block.
can_read
except check for handles that can be written to.
can_read
except check for handles that have an error condition, for example
EOF.
can_
methods is called or the object is passed to the select static method.
select()
call.
select()
call.
new
. READ
, WRITE
and ERROR
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 error conditions respectively. Upon error an empty array 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 = new IO::Socket::INET(Listen => 1, LocalPort => 8080); $sel = new IO::Select( $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 <Graham.Barr@tiuk.ti.com>
Copyright (c) 1995 Graham Barr. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.