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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
       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	(with $!  unchanged), in seconds, possibly fractional.	If
	   "TIMEOUT" is	not given and any handles are registered then the call
	   will	block indefinitely.  Upon error, an empty list is returned,
	   with	$! set to indicate the error.  To distinguish between timeout
	   and error, set $! to	zero before calling this method, and check it
	   after an empty list is returned.

       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.

	   If at least one handle is ready for the specified kind of
	   operation, 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
	   timeout, an empty list is returned, with $! unchanged.  Upon	error,
	   an empty list is returned, with $!  set to indicate the error.  To
	   distinguish between timeout and error, set $! to zero before
	   calling this	method,	and check it after 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	= IO::Socket::INET->new(Listen => 1, LocalPort => 8080);
	   $sel	= IO::Select->new( $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 <perlbug@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 v5.32.0			  2020-06-14			 IO::Select(3)

NAME | SYNOPSIS | DESCRIPTION | CONSTRUCTOR | METHODS | EXAMPLE | AUTHOR | COPYRIGHT

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