Event::io

📦 max

An io watcher: an event when a file descriptor is ready to read or to write, or has an exception pending - and, optionally, when it has been quiet for a given time. Its events are Event::Event::Io objects, whose got says what happened.

Event->io(%attributes) (or Event::io->new(...)) takes the shared attributes of Event::Watcher and the ones below. An io watcher repeats, and stays registered while its callback runs. Its default priority is PRIO_NORMAL. It refuses to start without a callback (“without io callback”), and with neither a descriptor to poll nor a timeout (“because there is nothing to watch”).

One watcher can watch for several conditions, or several watchers can share a descriptor; both work.

The bit constants R, W, E and T can be imported from Event::io as well as from Event::Watcher.

Synopsis

use Event;

Event->io(fd => \*STDIN, poll => 'r', timeout => 30,
    cb => sub {
        my $e = shift;
        if ($e->got =~ /t/) { print "30 seconds without input\n"; return }
        defined(my $line = <STDIN>) or return Event::unloop();
        print "read: $line";
    });
Event::loop();

Functions

Attributes

poll

What to wait for: a string of the letters r (read), w (write) and e (exception), or the number made of the bits R, W and E; "r" by default. Another letter warns “Ignored ‘x’ in poll mask” and other bits warn too. The value returned is both the string and the number. It includes t exactly when a timeout is set, whatever was asked.

fd

The descriptor to watch: a glob or glob reference (\*STDIN, an IO::Handle object), or a file descriptor number. Its descriptor is taken when the watcher starts; a glob without an open handle dies “isn’t a valid IO”, anything else “can’t find fileno”.

timeout

Seconds without a callback after which an event comes anyway, with t in its got; 0 or undef (the default) for none. Each callback restarts the count. A watcher that does not repeat fires the timeout once and then clears it.

timeout_cb

The callback for timeouts, in the forms cb takes; while it is undef (the default), timeouts go to cb too. Unlike cb, a [$object, $method_name] naming a method that does not exist is taken without a warning.