


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


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.



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


           "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 = 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);
                   }



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


                   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.






































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