Linux::FD::Event(3) Event filehandles for Linux


version 0.011


use Linux::FD::Event;

my $foo = Linux::FD::Event->new(42);
if (fork) {
say $foo->get while sleep 1
else {
$foo->add($_) while <>;


new($initial_value, @flags)

This creates an eventfd object that can be used as an event wait/notify mechanism by userspace applications, and by the kernel to notify userspace applications of events. The object contains an unsigned 64-bit integer counter that is maintained by the kernel. This counter is initialized with the value specified in the argument $initial_value. @flags is an optional list of flags, currently limited to 'non-blocking' (requires Linux 2.6.27), and 'semaphore' (requires Linux 2.6.30).


If the eventfd counter has a non-zero value, and 'semaphore' is not set, then a "get" returns 64 bit unsigned integer containing that value, and the counter's value is reset to zero. If 'semaphore' is set, it decrements the counter by one and returns one. In either case, if the counter is zero at the time of the "get", then the call either blocks until the counter becomes non-zero, or fails with the error EAGAIN if the file handle has been made non-blocking.


A "add" call adds the 64 bit unsigned integer value $value to the counter. The maximum value that may be stored in the counter is the largest unsigned 64-bit value minus 1 (i.e., 0xfffffffffffffffe). If the addition would cause the counter's value to exceed the maximum, then the "add" either blocks until a "get" is performed on the file descriptor, or fails with the error EAGAIN if the file descriptor has been made non-blocking. A "add" will fail with the error EINVAL if an attempt is made to write the value 0xffffffffffffffff.


Leon Timmermans <[email protected]>


This software is copyright (c) 2010 by Leon Timmermans.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.