Field exitCodeField = Shell.class.getDeclaredField("exitCode");
exitCodeField.setAccessible(true);
exitCodeField.set(nssd, 1);
// One single file fails to be accessed.
nssd.processErrorOutput(new ExitCodeException(1, "du: cannot access `a1.txt': No such file or directory"));
// Two files fail to be accessed
nssd.processErrorOutput(new ExitCodeException(1, "du: cannot access `a2.txt': No such file or directory\ndu: cannot access `a3.txt': No such file or directory"));
// Two files fail to be accessed, one is the same as the previous one