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 speci
fied 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.
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 frac
tional. 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, 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 ref
erence to an array which will hold the handles that
are ready for reading, writing and have error condi
tions 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;
$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.
2001-03-18 perl v5.6.1 IO::Select(3)
