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