Signals package

The Signals package provides support for handling Unix style signals. For each signal that you want to handle, you need to create a SignalHandler and a corresponding SignalNotify object. Each SignalHandler runs as it own actor and upon receiving the signal will call its corresponding SignalNotify's apply method.

Example program

The following program will listen for the TERM signal and output a message to standard out if it is received.

use "signals"

actor Main
  new create(env: Env) =>
    // Create a TERM handler
    let signal = SignalHandler(TermHandler(env), Sig.term())
    // Raise TERM signal
    signal.raise()

class TermHandler is SignalNotify
  let _env: Env

  new iso create(env: Env) =>
    _env = env

  fun ref apply(count: U32): Bool =>
    _env.out.print("TERM signal received")
    true

Signal portability

The Sig primitive provides support for portable signal handling across Linux, FreeBSD and OSX. Signals are not supported on Windows and attempting to use them will cause a compilation error.

Shutting down handlers

Unlike a TCPConnection and other forms of input receiving, creating a SignalHandler will not keep your program running. As such, you are not required to call dispose on your signal handlers in order to shutdown your program.

Public Types

• interface SignalNotify
• primitive SignalRaise
• actor SignalHandler
• primitive Sig