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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 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 = 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.

Index for Section 3

Alphabetical listing for I

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