Struct signal_hook::iterator::Signals

pub struct Signals { /* fields omitted */ }

The main structure of the module, representing interest in some signals.

Unlike the helpers in other modules, this registers the signals when created and unregisters them on drop. It provides the pending signals during its lifetime, either in batches or as an infinite iterator.

Multiple consumers

You may have noticed this structure can be used simultaneously by multiple threads. If it is done, a signal arrives to one of the threads (on the first come, first serve basis). The signal is not broadcasted to all currently active threads.

A similar thing applies to cloning the structure ‒ at least one of the copies gets the signal, but it is not broadcasted to all of them.

If you need multiple recipients, you can create multiple independent instances (not by cloning, but by the constructor).

Examples

use signal_hook::iterator::Signals;

let signals = Signals::new(&[signal_hook::SIGUSR1, signal_hook::SIGUSR2])?;
thread::spawn(move || {
    for signal in &signals {
        match signal {
            signal_hook::SIGUSR1 => {},
            signal_hook::SIGUSR2 => {},
            _ => unreachable!(),
        }
    }
});

mio support

If the crate is compiled with the mio-support or mio-0_7-support flags, the Signals becomes pluggable into mio version 0.6 or 0.7 respectively (it implements the Source trait). If it becomes readable, there may be new signals to pick up. The structure is expected to be registered with level triggered mode.

tokio support

If the crate is compiled with the tokio-support flag, the into_async method becomes available. This method turns the iterator into an asynchronous stream of received signals.

Methods

impl Signals

pub fn into_async(self) -> Result<Async, Error>

Turns the iterator into an asynchronous stream.

This allows getting the signals in asynchronous way in a tokio event loop. Available only if compiled with the tokio-support feature enabled.

Examples

extern crate libc;
extern crate signal_hook;
extern crate tokio;

use std::io::Error;

use signal_hook::iterator::Signals;
use tokio::prelude::*;

fn main() -> Result<(), Error> {
    let wait_signal = Signals::new(&[signal_hook::SIGUSR1])?
        .into_async()?
        .into_future()
        .map(|sig| assert_eq!(sig.0.unwrap(), signal_hook::SIGUSR1))
        .map_err(|e| panic!("{}", e.0));
    unsafe { libc::raise(signal_hook::SIGUSR1) };
    tokio::run(wait_signal);
    Ok(())
}

pub fn into_async_with_handle(self, handle: &Handle) -> Result<Async, Error>

Turns the iterator into a stream, tied into a specific tokio reactor.

impl Signals

pub fn new<I, S>(signals: I) -> Result<Self, Error> where
    I: IntoIterator<Item = S>,
    S: Borrow<c_int>, 

Creates the Signals structure.

This registers all the signals listed. The same restrictions (panics, errors) apply as with register.

pub fn add_signal(&self, signal: c_int) -> Result<(), Error>

Registers another signal to the set watched by this Signals instance.

Notes

• This is safe to call concurrently from whatever thread.
• This is not safe to call from within a signal handler.
• If the signal number was already registered previously, this is a no-op.
• If this errors, the original set of signals is left intact.
• This actually registers the signal into the whole group of Signals cloned from each other, so any of them might start receiving the signals.

Panics

• If the given signal is [forbidden][::FORBIDDEN].
• If the signal number is negative or larger than internal limit. The limit should be larger than any supported signal the OS supports.

pub fn pending(&self) -> Pending

Returns an iterator of already received signals.

This returns an iterator over all the signal numbers of the signals received since last time they were read (out of the set registered by this Signals instance). Note that they are returned in arbitrary order and a signal number is returned only once even if it was received multiple times.

This method returns immediately (does not block) and may produce an empty iterator if there are no signals ready.

pub fn wait(&self) -> Pending

Waits for some signals to be available and returns an iterator.

This is similar to pending. If there are no signals available, it tries to wait for some to arrive. However, due to implementation details, this still can produce an empty iterator.

This can block for arbitrary long time.

Note that the blocking is done in this method, not in the iterator.

pub fn forever(&self) -> Forever

Returns an infinite iterator over arriving signals.

The iterator's next() blocks as necessary to wait for signals to arrive. This is adequate if you want to designate a thread solely to handling signals. If multiple signals come at the same time (between two values produced by the iterator), they will be returned in arbitrary order. Multiple instances of the same signal may be collated.

This is also the iterator returned by IntoIterator implementation on &Signals.

This iterator terminates only if the Signals is explicitly closed.

Examples

use signal_hook::iterator::Signals;

let signals = Signals::new(&[signal_hook::SIGUSR1, signal_hook::SIGUSR2])?;
thread::spawn(move || {
    for signal in signals.forever() {
        match signal {
            signal_hook::SIGUSR1 => {},
            signal_hook::SIGUSR2 => {},
            _ => unreachable!(),
        }
    }
});

pub fn is_closed(&self) -> bool

Is it closed?

See close.

pub fn close(&self)

Closes the instance.

This is meant to signalize termination through all the interrelated instances ‒ the ones created by cloning the same original Signals instance (and all the Async ones created from them). After calling close:

• is_closed will return true.
• All currently blocking operations on all threads and all the instances are interrupted and terminate.
• Any further operations will never block.
• Further signals may or may not be returned from the iterators. However, if any are returned, these are real signals that happened.
• The forever terminates (follows from the above).

The goal is to be able to shut down any background thread that handles only the signals.

let signals = Signals::new(&[SIGUSR1])?;
let signals_bg = signals.clone();
let thread = std::thread::spawn(move || {
    for signal in &signals_bg {
        // Whatever with the signal
    }
});

signals.close();

// The thread will terminate on its own now (the for cycle runs out of signals).
thread.join().expect("background thread panicked");

Trait Implementations

impl Clone for Signals

fn clone(&self) -> Signals

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Signals

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Evented for Signals

fn register(
    &self,
    poll: &Poll,
    token: Token,
    interest: Ready,
    opts: PollOpt
) -> Result<(), Error>

Register self with the given Poll instance.

fn reregister(
    &self,
    poll: &Poll,
    token: Token,
    interest: Ready,
    opts: PollOpt
) -> Result<(), Error>

Re-register self with the given Poll instance.

fn deregister(&self, poll: &Poll) -> Result<(), Error>

Deregister self from the given Poll instance

impl<'a> IntoIterator for &'a Signals

type Item = c_int

The type of the elements being iterated over.

type IntoIter = Forever<'a>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Forever<'a>

Creates an iterator from a value.

impl Source for Signals

fn register(
    &mut self,
    registry: &Registry,
    token: Token,
    interest: Interest
) -> Result<(), Error>

Register self with the given Registry instance.

fn reregister(
    &mut self,
    registry: &Registry,
    token: Token,
    interest: Interest
) -> Result<(), Error>

Re-register self with the given Registry instance.

fn deregister(&mut self, registry: &Registry) -> Result<(), Error>

Deregister self from the given Registry instance.