How to Gracefully Handle Ctrl C Interrupts in CLI Java Applications?

Capturing Ctrl C Interrupts in CLI Java Applications

In CLI Java applications, intercepting the Ctrl C signal (usually terminating the process) can be crucial for handling user input gracefully. This article addresses how to achieve this interception across multiple platforms.

Multi-Platform Solution

To intercept Ctrl C signals consistently across Linux, Solaris, and Windows, the recommended approach is using a SignalHandler. The sun.misc.SignalHandler class provides this functionality. By implementing SignalHandler#handle and registering it for the SIGINT signal, you can capture the interrupt and execute custom code.

Implementation

Here's an example of how to use a SignalHandler in Java:

<code class="java">import sun.misc.Signal;
import sun.misc.SignalHandler;

public class CtrlCHandler {

    public static void main(String[] args) {
        // Register a SignalHandler for SIGINT (Ctrl+C)
        Signal.handle(new Signal("INT"), new SignalHandler() {
            @Override
            public void handle(Signal signal) {
                // Custom shutdown code here
                System.out.println("Ctrl+C received, performing shutdown...");
                Runtime.getRuntime().exit(0);
            }
        });

        // Other application logic here...
    }
}</code>

Note that this method will intercept the signal only as an intermediate step before the JVM shuts down completely, so it may not be suitable for all use cases.

Alternatively:

If using a SignalHandler is not feasible, consider using the Runtime.getRuntime().addShutdownHook method. This allows you to register a Thread that will be executed when the JVM is shutting down. Within this thread, you can handle the Ctrl C interrupt and perform any necessary cleanup or shutdown procedures.

<code class="java">Runtime.getRuntime().addShutdownHook(new Thread() {
    public void run() {
        // Custom shutdown code here
        System.out.println("JVM shutting down...");
    }
});</code>

These methods provide flexible solutions for intercepting Ctrl C signals in CLI Java applications, enabling you to handle user input gracefully and perform custom actions before process termination.

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