NAME
IO::Select - OO interface to the select system call
SYNOPSIS
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);
DESCRIPTION
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.
CONSTRUCTOR
- new ( [ HANDLES ] )
The constructor creates a new object and optionally initialises it with a set of handles.
METHODS
- add ( HANDLES )
Add the list of handles to the
IO::Selectobject. It is these values that will be returned when an event occurs.IO::Selectkeeps these values in a cache which is indexed by thefilenoof the handle, so if more than one handle with the samefilenois specified then only the last one is cached.Each handle can be an
IO::Handleobject, an integer or an array reference where the first element is anIO::Handleor an integer. - remove ( HANDLES )
Remove all the given handles from the object. This method also works by the
filenoof the handles. So the exact handles that were added need not be passed, just handles that have an equivalentfileno - 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.
TIMEOUTis the maximum amount of time to wait before returning an empty list, in seconds, possibly fractional. IfTIMEOUTis not given and any handles are registered then the call will block. - can_write ( [ TIMEOUT ] )
Same as
can_readexcept check for handles that can be written to. - has_exception ( [ TIMEOUT ] )
Same as
can_readexcept 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 theselectstatic method. - bits()
Return the bit string suitable as argument to the core select() call.
- select ( READ, WRITE, EXCEPTION [, TIMEOUT ] )
selectis a static method, that is you call it with the package name likenew.READ,WRITEandEXCEPTIONare eitherundeforIO::Selectobjects.TIMEOUTis 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.
EXAMPLE
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;
}
}
}AUTHOR
Graham Barr. Currently maintained by the Perl Porters. Please report all bugs to <perl5-porters@perl.org>.
COPYRIGHT
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.

