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#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

TheIO::Select package implements an object approach to the systemselect function call. It allows the user to see what IO handles, seeIO::Handle, 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 theIO::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 thefileno of the handle, so if more than one handle with the samefileno is specified then only the last one is cached.

Each handle can be anIO::Handle object, an integer or an array reference where the first element is anIO::Handle or an integer.

#remove ( HANDLES )

Remove all the given handles from the object. This method also works by thefileno of the handles. So the exact handles that were added need not be passed, just handles that have an equivalentfileno

#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 fractional. IfTIMEOUT is not given and any handles are registered then the call will block.

#can_write ( [ TIMEOUT ] )

Same ascan_read except check for handles that can be written to.

#has_exception ( [ TIMEOUT ] )

Same ascan_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 thecan_ methods is called or the object is passed to theselect 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 likenew.READ,WRITE andERROR are eitherundef orIO::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 howIO::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

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