Exit in Kotlin

Here’s an idiomatic Kotlin example demonstrating the concept of program exit:

import kotlin.system.exitProcess

fun main() {
    // This will not be executed due to the immediate exit
    Runtime.getRuntime().addShutdownHook(Thread {
        println("Shutdown hook will not run!")
    })

    // Exit the program with status code 3
    exitProcess(3)
}

This Kotlin program demonstrates how to exit a program immediately with a specific status code. Let’s break down the code and explain its components:

1. We import exitProcess from the kotlin.system package, which allows us to exit the program with a specific status code.

2. In the main function, we first add a shutdown hook using Runtime.getRuntime().addShutdownHook(). This is similar to using defer in Go, but it’s important to note that shutdown hooks in Kotlin are not guaranteed to run when using exitProcess().

3. We then call exitProcess(3), which immediately terminates the program with a status code of 3. This is equivalent to os.Exit(3) in Go.

To run this Kotlin program:

1. Save the code in a file named ExitExample.kt.
2. Compile and run the program using the Kotlin compiler:

$ kotlinc ExitExample.kt -include-runtime -d ExitExample.jar
$ java -jar ExitExample.jar
$ echo $?
3

The echo $? command displays the exit status of the last executed command, which in this case is 3.

Note that the shutdown hook message is not printed because exitProcess() terminates the program immediately without running shutdown hooks or finalizers.

In Kotlin, like in Java, the main function doesn’t return an integer to indicate the exit status. Instead, we use exitProcess() to exit with a non-zero status code.

This example demonstrates how to handle program exit in Kotlin, which is conceptually similar to the Go example but uses Kotlin-specific syntax and idioms.