signal

The signal package runs your code when the process receives SIGINT (Ctrl+C), SIGTERM or SIGHUP. Handlers run on a background task.

signal::trap(signal::SIGINT, with () do
  println "Shutting down..."
  exit 0
end)

println "Running. Press Ctrl+C to stop."
while true do
  task::sleep(100)
end

Registering a handler replaces the default behavior for that signal: after trapping SIGINT, Ctrl+C no longer stops the program unless the handler calls exit.

Function	Does
trap(signal, handler)	Runs handler when the signal arrives.
reset(signal)	Removes the handler and restores the default behavior.
trapped(signal)	Whether a handler is registered.
raise_signal(signal)	Runs the handler as if the signal had arrived; useful in tests.

signal::trap(signal::SIGHUP, with () do
  println "reloading configuration"
end)

signal::raise_signal(signal::SIGHUP)
task::sleep(100)                       # give the background handler time to run

println signal::trapped(signal::SIGHUP)   # true
signal::reset(signal::SIGHUP)

signal is unavailable in safe mode. On Windows only SIGINT is delivered.

Constants

Name	Value	Description
signal::SIGINT	"SIGINT"
signal::SIGTERM	"SIGTERM"
signal::SIGHUP	"SIGHUP"

Functions

signal::trap

signal::trap(sig, handler)

Registers a signal handler. The callback runs asynchronously in a background task.

Parameter	Type	Default	Description
sig	string		Signal name (e.g., signal::SIGINT, "SIGTERM").
handler	lambda		Zero-argument lambda invoked when the signal fires.

import signal
signal::trap(signal::SIGINT, fn()
  println "Shutting down..."
  exit(0)
end)
println "Running. Press Ctrl+C to stop."
while true do
  task::sleep(100)
end

signal::reset

signal::reset(sig)

Removes a signal handler.

Parameter	Type	Default	Description
sig	string		Signal name.

signal::trapped

signal::trapped(sig)

Returns true if a signal handler is registered for the given signal.

Parameter	Type	Default	Description
sig	string		Signal name.

Returns boolean

signal::raise_signal

signal::raise_signal(sig)

Programmatically fires a signal (useful for testing handlers).

Parameter	Type	Default	Description
sig	string		Signal name.