This crate has reached its end-of-life and is now deprecated.
The intended successor of the chan
crate is the
crossbeam-channel
crate. Its API is strikingly similar, but comes with a much better select!
macro, better performance, a better test suite and an all-around better
implementation.
If you were previously using this crate for signal handling, then it is
simple to reproduce a similar API with crossbeam-channel
and the
signal-hook
crate. For example, here's chan-signal
's notify
function:
extern crate crossbeam_channel as channel;
extern crate signal_hook;
fn notify(signals: &[c_int]) -> Result<channel::Receiver<c_int>> {
let (s, r) = channel::bounded(100);
let signals = signal_hook::iterator::Signals::new(signals)?;
thread::spawn(move || {
for signal in signals.forever() {
if s.send(signal).is_err() {
break;
}
}
});
Ok(r)
}
This crate may continue to receive bug fixes, but should otherwise be considered dead.
chan-signal
This crate provies experimental support for responding to OS signals using channels. Currently, this only works on Unix based systems, but I'd appreciate help adding Windows support.
Dual-licensed under MIT or the UNLICENSE.
Documentation
Example
Use is really simple. Just ask the chan_signal
crate to create a channel
subscribed to a set of signals. When a signal is sent to the process it will
be delivered to the channel.
use chan_signal::Signal;
let signal = chan_signal::notify(&[Signal::INT, Signal::TERM]);
// Blocks until this process is sent an INT or TERM signal.
// Since the channel is never closed, we can unwrap the received value.
signal.recv().unwrap();
A realer example
When combined with chan_select!
from the chan
crate, one can easily
integrate signals with the rest of your program. For example, consider a
main function that waits for either normal completion of work (which is done
in a separate thread) or for a signal to be delivered:
#[macro_use]
extern crate chan;
extern crate chan_signal;
use std::thread;
use std::time::Duration;
use chan_signal::Signal;
fn main() {
// Signal gets a value when the OS sent a INT or TERM signal.
let signal = chan_signal::notify(&[Signal::INT, Signal::TERM]);
// When our work is complete, send a sentinel value on `sdone`.
let (sdone, rdone) = chan::sync(0);
// Run work.
thread::spawn(move || run(sdone));
// Wait for a signal or for work to be done.
chan_select! {
signal.recv() -> signal => {
println!("received signal: {:?}", signal)
},
rdone.recv() => {
println!("Program completed normally.");
}
}
}
fn run(_sdone: chan::Sender<()>) {
println!("Running work for 5 seconds.");
println!("Can you send a signal quickly enough?");
// Do some work.
thread::sleep(Duration::from_secs(5));
// _sdone gets dropped which closes the channel and causes `rdone`
// to unblock.
}
This is much easier than registering a signal handler because:
- Signal handlers run asynchronously.
- The code you're permitted to execute in a signal handler is extremely constrained (e.g., no allocation), so it is difficult to integrate it with the rest of your program.
Using channels, you can invent whatever flow you like and handle OS signals just like anything else.
How it works
TL;DR - Spawn a thread, block on sigwait
, deliver signals, repeat.