Signals in Wolfram Language

Here’s an idiomatic example in Wolfram Language that demonstrates handling signals, similar to the concept shown in the Go example:

(* Import necessary symbols *)
Needs["JLink`"]

(* Create a function to handle the signal *)
handleSignal[sig_] := (
  Print[];
  Print["Received signal: ", sig];
  signalReceived = True;
)

(* Set up signal handlers *)
InstallJava[];
LoadJavaClass["java.lang.Runtime"];
runtime = JLink`JavaNew["java.lang.Runtime"];
JLink`JavaBlock[
  shutdownHook = JLink`JavaNew["java.lang.Thread", 
    JLink`JavaNew["java.lang.Runnable", Function[handleSignal["SIGTERM"]]]
  ];
  runtime@addShutdownHook[shutdownHook];
]

(* Main program loop *)
signalReceived = False;
Print["Awaiting signal..."];
While[!signalReceived,
  Pause[1];  (* Sleep for 1 second *)
]
Print["Exiting"];

This Wolfram Language script demonstrates how to handle signals, specifically focusing on the SIGTERM signal. Here’s a breakdown of the code:

1. We import the necessary symbols from the JLink` package, which allows us to interact with Java classes.

2. We define a handleSignal function that prints the received signal and sets a flag indicating that a signal was received.

3. We set up the Java runtime and create a shutdown hook. This hook will be called when the program receives a SIGTERM signal.

4. In the main program loop, we continuously check if a signal has been received. The program will keep running until it receives a signal.

To run this script:

1. Save the code in a file, e.g., signal_handler.wl.
2. Open a Wolfram Language kernel or Mathematica notebook.
3. Execute the script using <<signal_handler.wl.

The program will print “Awaiting signal…” and then wait. To test it, you can send a SIGTERM signal to the process. On Unix-like systems, you can do this by finding the process ID (PID) of the Wolfram kernel and using the kill command:

$ kill -SIGTERM <PID>

The program will then print the received signal and exit.

Note that the Wolfram Language doesn’t have built-in functions for handling Unix signals like Go does. Instead, we use Java’s shutdown hook mechanism through JLink to achieve similar functionality. This approach allows us to handle SIGTERM, but other signals like SIGINT might require different methods or external tools.

Remember that this script needs to be run in an environment where Java is available and accessible to the Wolfram Language kernel.