Signals in Chapel

Here’s the translation of the Go code to Chapel, formatted in Markdown suitable for Hugo:

Our first example demonstrates how to handle signals in Chapel. This can be useful for gracefully shutting down a server when it receives a SIGTERM, or stopping a command-line tool from processing input when it receives a SIGINT.

use OS, IO, Time;

proc main() {
    // Chapel doesn't have a direct equivalent to Go's signal channels,
    // so we'll use a boolean flag to simulate signal handling
    var shouldExit: atomic bool = false;

    // Start a task to handle the signal
    begin {
        // Simulate waiting for a signal
        sleep(5);
        writeln();
        writeln("Received signal");
        shouldExit.write(true);
    }

    // Main program logic
    writeln("awaiting signal");
    while (!shouldExit.read()) {
        // Simulate doing work
        sleep(1);
    }
    writeln("exiting");
}

In this Chapel program:

1. We use the OS, IO, and Time modules for system operations, input/output, and time-related functions.

2. Instead of using channels for signal notification, we use an atomic boolean variable shouldExit to coordinate between the main program and the signal handling task.

3. We start a separate task (similar to a goroutine) using the begin statement. This task simulates waiting for a signal by sleeping for 5 seconds, then sets the shouldExit flag.

4. The main program enters a loop, checking the shouldExit flag periodically. This simulates waiting for a signal while potentially doing other work.

5. When the “signal” is received (simulated by the separate task), the program exits the loop and terminates.

To run this program:

$ chpl signals.chpl -o signals
$ ./signals
awaiting signal

Received signal
exiting

In this example, the program waits for 5 seconds (simulating waiting for a signal), then prints “Received signal” and exits.

Note that Chapel doesn’t have built-in signal handling like Go does. In a real-world scenario, you would need to use Chapel’s extern blocks to interface with C libraries for actual signal handling. This example provides a simplified simulation of the concept.