Question

I run egrep using Java Runtime.exec()

String command = "egrep \'(Success|Loading\\.\\.\\.|Loaded : READY|Found a running instance)\' "+ instance.getPath() + "/log";
Runtime.getRuntime().exec(command);

The stdout is always null and stderr shows “egrep: Unmatched ( or (“. but when I copy the command to shell and run, it returns the correct value.

Answer 1

The solution is pretty simple: (Success|Loading\\.\\.\\.|Loaded is not a valid regex.

You can’t protect white space with quotes when using Process.exec(String). Always use the versions of exec() that take an array or, even better, use ProcessBuilder.

That way, you can pass each argument as a single Java String and spaces and other special characters won’t create any problems.