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 IO::Handle,
are ready for reading, writing or have an exception pending.
The constructor creates a new object and optionally initialises it with a set of 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 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
Returns a true value (actually the handle itself) if it is present. Returns undef otherwise.
Return an array of all registered handles.
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.
Same as can_read
except check for handles that can be written to.
Same as can_read
except check for handles that have an exception
condition, for example pending out-of-band data.
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.
Return the bit string suitable as argument to the core select() call.
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 <perl5-porters@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.