执行命令行，cd不起作用

Question

I'm trying to execute cd using

    try {
        Process process = Runtime.getRuntime().exec(command);
        BufferedReader stream = new BufferedReader(new InputStreamReader(process.getInputStream()));
        String line;
        while ((line = stream.readLine()) != null) {
            stringBuilder.append(line);
            stringBuilder.append('\n');
        }
        stream = new BufferedReader(new InputStreamReader(process.getErrorStream()));
        while ((line = stream.readLine()) != null) {
            stringBuilder.append(line);
            stringBuilder.append('\n');
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

ls works. But cd dir doesn't work. It doesn't change the directory. If I execute pwd , it still shows / . I read that each time Runtime.getRuntime().exec(command); is executed, it creates a new shell. I think I need to capture that shell some how and maintain it till the user closes the app.

Not just that, I'm not getting any errors in my output. Eg. when I put a command that does not exist, I don't get the error message.

Answer 1

I read that each time Runtime.getRuntime().exec(command); is executed, it creates a new shell.

That is correct. When you call Runtime.exec() for each command, you are creating a new process. Each process gets its own environment, including a separate working directory which does not affect the parent process (your app), or any other processes you create afterwards.

I'm not getting any errors in my output

You don't get any errors because the shell commands do not fail to execute. The commands simply return a status code indicating success or failure when the process terminates - the code can be obtained via Process.exitValue() - but make sure the process has finished first using Process.waitFor() .

If you want to execute multiple commands, you could use exec() to launch a shell executable and then write commands and read replies via the input and output streams, or just join all the commands together using semicolons and execute them directly using a command line like:

sh -c 'cd /;pwd'