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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)->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 the IO::Handle manpage, 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 a
         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. 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_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 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.



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.









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