How to handle Ctrl-C in Java with child process?

Question

I'm facing an annoying issue with Java and I couldn't find a solution.

In my code, I create a subprocess to validate a git commit like this:

void processCommit(String commitId) throws InterruptedException, IOException {
    int result = new ProcessBuilder("git", "cat-file", "-e", commitId + "^{commit}").start().waitFor();
    if (result != 0) {
        throw new IllegalArgumentException("Invalid commit '" + commitId + "'!");
    }
    // further processing
}

Git will have a 0 exit status if commitId denotes a valid commit. Otherwise, I know the commit doesn't exist and I throw an appropriate exception.

However, when processing multiple commits and the process is long-running, when I type Ctrl-C into the terminal, the JVM exits by throwing an Invalid commit ...! exception.

This happens because the SIGINT signal is sent to all child processes of the JVM, not only to the JVM itself. There is probably a race condition:

the git child process is killed and exits with non-zero status
before the JVM is killed, the exception is thrown and shuts down the JVM

This happens under Linux, I didn't try on Windows, but my guess is that the behavior would be similar.

Trying to register a shutdown hook didn't help.

While this is a rather cosmetic issue, it really bugs me. How can I gracefully handle this and not report that a commit doesn't exist upon a Ctrl-C, but rather terminate the JVM either with no error message, or at least with an InterruptedException?

Thanks!

According to https://stackoverflow.com/questions/11119970/java-processbuilder-exitvalues a process killed by SIGINT will result in ProcessBuilder returning 130 (128+2). — Mark Plotnick, Nov 06 '17 at 03:01
That's an option (though I have to rely on the VCS subprocess to behave properly and not exit with that exit code for any other reason, but this seems reasonable). Do you know by any means where I can find the documented exit code for Ctrl-C on Windows (I would like my program to be cross-platform)? Trying to Ctrl-C on Windows leads to an exit code of `-1073741510`, but I couldn't find that value documented anywhere, so I'm not sure how reliable it is. Thanks! — Andrei Heidelbacher, Nov 06 '17 at 11:13

How to handle Ctrl-C in Java with child process?

0 Answers0