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

       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)->can_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 IO::Handle, are ready for read-
       ing, writing or have an exception 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 speci-
           fied 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.

           Return an array of all registered handles.

       can_read ( [ TIMEOUT ] )
           Return an array of handles that are ready for reading.

perl v5.8.5                 2002-11-06                          1

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 frac-
           tional. 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.

           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 ref-
           erence 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.

       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 );

perl v5.8.5                 2002-11-06                          2

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

           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. Currently maintained by the Perl Porters.
       Please report all bugs to <perl5-portersATperl.org>.

       Copyright (c) 1997-8 Graham Barr <gbarrATpobox.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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