IO::Select(3) 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)->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 the
IO::Handle manpage, are ready for reading, writing or have an error
condition 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 a 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.
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IO::Select(3) IO::Select(3)
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. 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_error ( [ TIMEOUT ] )
Same as can_read except check for handles that have an error
condition, for example EOF.
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.
bits()
Return the bit string suitable as argument to the core select() call.
select ( READ, WRITE, ERROR [, TIMEOUT ] )
select is a static method, that is you call it with the package name
like new. READ, WRITE and ERROR 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 error conditions respectively. Upon error an empty array 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;
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IO::Select(3) IO::Select(3)
$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 <Graham.Barr@tiuk.ti.com>
COPYRIGHT
Copyright (c) 1995 Graham Barr. 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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