MirBSD manpage: IO::Select(3p)

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 reading,
     writing or have an exception pending.


     new ( [ HANDLES ] )
         The constructor creates a new object and optionally ini-
         tialises 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 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.

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

     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 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

     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 "EXCEP-
         TION" 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 refer-
         ence to an array which will hold the handles that are
         ready for reading, writing and have exceptions respec-
         tively. 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 );

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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-porters@perl.org>.


     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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