IO::Select
See the current Perl documentation for IO::Select.
Here is our local, out-dated (pre-5.6) version:
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(@ha
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.
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::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 aIO::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. IfTIMEOUT
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_error ( [ TIMEOUT ] )
-
Same as
can_read
except check for handles that have an error condition, for example EOF. - 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. - bits()
-
Return the bit string suitable as argument to the core
select()
call. - select ( READ, WRITE, ERROR [, TIMEOUT ] )
-
select is a static method, that is you call it with the package name like
new
.READ
,WRITE
andERROR
are either undef orIO::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.
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 <Graham.Barr@tiuk.ti.com>
COPYRIGHT
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.