Doing Something Before Program Exit

Doing something before program exit

Check out the atexit module:

http://docs.python.org/library/atexit.html

For example, if I wanted to print a message when my application was terminating:

import atexit

def exit_handler():
    print 'My application is ending!'

atexit.register(exit_handler)

Just be aware that this works great for normal termination of the script, but it won't get called in all cases (e.g. fatal internal errors).

C: Doing something when the program exits

look into the atexit API of the C standard library.

How to run code before program exit?

Try the ProcessExit event of AppDomain:

using System;
class Test {
    static void Main(string[] args)
    {
        AppDomain.CurrentDomain.ProcessExit += new EventHandler (OnProcessExit); 
        // Do something here
    }

    static void OnProcessExit (object sender, EventArgs e)
    {
        Console.WriteLine ("I'm out of here");
    }
}

Why does this program exit before invoking my then clause?

As in the answer to your previous question, you are using a Promise, which is guaranteed to skip over the request and response. By passing in those two functions, you are offering your execution environment (presumably Node) callbacks that it can call once it successfully completes the request. Because you're accessing a remote server, this will take some time, typically in the tens or hundreds of milliseconds.

If you don't instruct Node otherwise, it will terminate when it reaches the end of your script. This may not be in time for the library to invoke your callback. As in this NodeJS issue, you can use a top-level await function, which pauses execution of your program to wait for the callback.

try {
  let success = await request(options);
  console.log(success);
} catch (error) {
  console.log('noob!');
}

See also: Node exits without error and doesn't await promise (Event callback)

Calling function when program exits in java

You can add a shutdown hook to your application by doing the following:

Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
    public void run() {
        // what you want to do
    }
}));

This is basically equivalent to having a try {} finally {} block around your entire program, and basically encompasses what's in the finally block.

Please note the caveats though!

Running code on program exit in Java

Use Runtime.getRuntime().addShutdownHook(Thread).

Doing a cleanup action just before Node.js exits

UPDATE:

You can register a handler for process.on('exit') and in any other case(SIGINT or unhandled exception) to call process.exit()

process.stdin.resume();//so the program will not close instantly

function exitHandler(options, exitCode) {
    if (options.cleanup) console.log('clean');
    if (exitCode || exitCode === 0) console.log(exitCode);
    if (options.exit) process.exit();
}

//do something when app is closing
process.on('exit', exitHandler.bind(null,{cleanup:true}));

//catches ctrl+c event
process.on('SIGINT', exitHandler.bind(null, {exit:true}));

// catches "kill pid" (for example: nodemon restart)
process.on('SIGUSR1', exitHandler.bind(null, {exit:true}));
process.on('SIGUSR2', exitHandler.bind(null, {exit:true}));

//catches uncaught exceptions
process.on('uncaughtException', exitHandler.bind(null, {exit:true}));

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