IO::Select(3)          Perl Programmers Reference Guide          IO::Select(3)

       IO::Select - OO interface to the select system call

           use IO::Select;

           $s = IO::Select->new();


           @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
       the IO::Handle manpage, are ready for reading, writing or have an error
       condition pending.

       new ( [ HANDLES ] )
           The constructor creates a new object and optionally initialises it
           with a set of handles.

       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

       exists ( HANDLE )
           Returns a true value (actually the handle itself) if it is present.
           Returns undef otherwise.

           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.

           Return the bit string suitable as argument to the core select()

           Return the bit string suitable as argument to the core select()

       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.

       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;
                   else {
                       # Process socket

                       # Maybe we have finished with the socket

       Graham Barr <>

       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.

3rd Berkeley Distribution    perl 5.005, patch 02                IO::Select(3)