Signals in Nim

Here’s the translation of the Go code to Nim, along with explanations in Markdown format suitable for Hugo:

Our program demonstrates how to handle Unix signals in Nim. For example, we might want a server to gracefully shutdown when it receives a SIGTERM, or a command-line tool to stop processing input if it receives a SIGINT. Here’s how to handle signals in Nim.

import os, posix

proc handleSignal() {.noconv.} =
  echo()
  echo "Received signal"
  quit(0)

setControlCHook(handleSignal)

echo "awaiting signal"
while true:
  sleep(1000)

Nim signal handling works by setting up a callback function that will be called when a signal is received. We’ll create a procedure to handle these signals.

The handleSignal procedure is defined with the noconv pragma, which is necessary for signal handling functions in Nim.

We use setControlCHook to register our handler for the SIGINT signal (which is typically sent when the user presses Ctrl+C).

The program will then enter an infinite loop, waiting for a signal. When a signal is received, our handler will be called, which will print a message and then exit the program.

When we run this program it will block waiting for a signal. By typing ctrl-C (which the terminal shows as ^C) we can send a SIGINT signal, causing the program to print the message and then exit.

$ nim c -r signals.nim
awaiting signal
^C
Received signal

In this Nim version, we’ve simplified the signal handling to focus on SIGINT (Ctrl+C). Nim’s standard library doesn’t provide a direct equivalent to Go’s signal.Notify for multiple signals, but you can set up multiple signal handlers using the system.setSignalHandler function if needed.

The concept of channels and goroutines doesn’t have a direct equivalent in Nim, so we’ve used a simpler approach with a blocking loop and a signal handler. This achieves a similar effect of waiting for and responding to signals.