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



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::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 ( 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, in seconds, possibly fractional. 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_exception ( [ TIMEOUT ] )
           Same as "can_read" except 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 the "select" static method.

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

       select ( READ, WRITE, EXCEPTION [, TIMEOUT ] )
           "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.

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 = 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;
                   }
               }
           }

AUTHOR
       Graham Barr. Currently maintained by the Perl Porters.  Please report all bugs to <perlbug@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.



perl v5.16.2                                     2012-10-11                                  IO::Select(3pm)