@Test
	public void testLocalEchoOff() throws IOException {
		try (UnixPty pty = openpty()) {
			pty.getChild().nullSession(Echo.OFF);

			PrintWriter writerP = new PrintWriter(pty.getParent().getOutputStream());
			PrintWriter writerC = new PrintWriter(pty.getChild().getOutputStream());
			BufferedReader reader =
				new BufferedReader(new InputStreamReader(pty.getParent().getInputStream()));

			writerP.println("Hello, World!");
			writerP.flush();
			writerC.println("Good bye!");
			writerC.flush();

			assertEquals("Good bye!", reader.readLine());
		}
	}
Choice of 127 is based on bash setting "exit code" to 127 for "command not found"
Ghidra/Framework/Pty/src/test/java/ghidra/pty/unix/AbstractUnixPtyTest.java