IO::Select

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



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 pend-
       ing.

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, writ-
           ing 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 lis-
       tening 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);
                   }
                   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.



perl v5.8.6                       2001-09-21                     IO::Select(3)