Java : Running shell script in background

Question

Im trying to run a shell script in the background that does not terminate when my function/process end. However it seems that despite nohup, when the java thread ends. So does the script.

Below is sample code.

///
/// Tries to run a script in the background
///
try {
    Runtime rt = Runtime.getRuntime();
    Process pr = rt.exec("nohup sh ./runner.sh > output.txt &", new String[] {}, wrkDir);
    // pr.waitFor(); // Intentionally not using
} catch(Exception e) {
    throw new RuntimeException(e);
}

Palpatim · Accepted Answer · 2016-12-22 15:59:33Z

nohup applies to invocations from the shell, not from a calling program.

There are probably a lot of ways to solve this, but one that springs to mind is to try modifying your Java code to invoke a launcher shell script that invokes the nohup runner.sh... code (without needing to launch sh).

Something like this (untested) code:

Revised Java:

///
/// Tries to run a script in the background
///
try {
    Runtime rt = Runtime.getRuntime();
    Process pr = rt.exec("sh ./launcher.sh", new String[] {}, wrkDir);
    // pr.waitFor(); // Intentionally not using
} catch(Exception e) {
    throw new RuntimeException(e);
}

launcher.sh

#!/bin/sh

nohup ./runner.sh > output.txt &

I'm not sure about the redirection here, but if this works (as I mentioned, this solution is untested), the downside would be that you lose feedback from attempting to invoke runner--any errors in that script invocation will be unavailable to your Java process.

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