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IO::Select

Section: Perl Programmers Reference Guide (3)
Updated: perl 5.004, patch 04
Index

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 selectfunction 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 setof handles.

METHODS

add ( HANDLES ): Add the list of handles to the IO::Select object. It is these values thatwill be returned when an event occurs. IO::Select keeps these values in acache which is indexed by the fileno of the handle, so if more than onehandle 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 arrayreference where the first element is a IO::Handle or an integer.
remove ( HANDLES ): Remove all the given handles from the object. This method also worksby the fileno of the handles. So the exact handles that were addedneed 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 isthe maximum amount of time to wait before returning an empty list. IfTIMEOUT is not given and any handles are registered then the callwill 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 errorcondition, for example EOF.
count (): Returns the number of handles that the object will check for whenone of the can_ methods is called or the object is passed tothe 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 packagename like new. READ, WRITE and ERROR are either undefor IO::Select objects. TIMEOUT is optional and has the sameeffect as for the core select call.
The result will be an array of 3 elements, each a reference to an arraywhich will hold the handles that are ready for reading, writing and haveerror conditions respectively. Upon error an empty array is returned.

EXAMPLE

Here is a short example which shows how IO::Select could be usedto write a server which communicates with several sockets while alsolistening 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 <Graham.BarrAATTtiuk.ti.com>

COPYRIGHT

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