signal

The signal package provides OS signal handling for SIGINT, SIGTERM, and SIGHUP. Handlers are registered with trap() and run asynchronously in a background task.

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Constants

Constant	Value	Description
signal::SIGINT	"SIGINT"	Interrupt (Ctrl+C)
signal::SIGTERM	"SIGTERM"	Termination request
signal::SIGHUP	"SIGHUP"	Hang-up / configuration reload

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Package Functions

trap(sig, handler)

Registers a handler for the given signal. The handler is invoked asynchronously in a background task when the signal fires.

Parameters

Type	Name	Description
string	sig	Signal name — use the constants or a string literal
lambda	handler	Zero-argument lambda: with () do ... end

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reset(sig)

Removes the handler for the given signal.

Parameters

Type	Name	Description
string	sig	Signal name

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trapped(sig)

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

Parameters

Type	Name	Description
string	sig	Signal name

Returns

Type	Description
boolean	true if a handler is registered

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raise_signal(sig)

Programmatically fires a signal. Useful for testing signal handlers.

Parameters

Type	Name	Description
string	sig	Signal name

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Examples

Graceful shutdown on Ctrl+C

import "signal"
import "task"

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

println "Running. Press Ctrl+C to stop."

while true do
  task::sleep(100)
end

Reload configuration on SIGHUP

import "signal"
import "task"

signal::trap(signal::SIGHUP, with () do
  println "Reloading configuration..."
  # reload_config()
end)

println "PID: ${sys::pid()}"

while true do
  task::sleep(500)
end

Cleanup on SIGTERM

import "signal"
import "task"

signal::trap(signal::SIGTERM, with () do
  println "SIGTERM received — cleaning up"
  # close connections, flush buffers, etc.
  exit(0)
end)

while true do
  task::sleep(100)
end

Testing a handler

import "signal"

signal::trap(signal::SIGINT, with () do
  println "Handler fired!"
end)

signal::raise_signal(signal::SIGINT)   # Fires the handler immediately
task::sleep(100)                       # Give the background task time to run