Question

Okay, so I have been experimenting with the Process and Runtime classes and I have run into a problem. When I try to execute this command : cmd /c dir, the output is null. Here is a snippet of my code:

try {
    Runtime runtime = Runtime.getRuntime();
    Process process = runtime.exec("cmd /c dir");

    BufferedReader output = new BufferedReader(new InputStreamReader(process.getInputStream()));

    //BufferedReader serverOutputError = new BufferedReader(new InputStreamReader(serverStart.getErrorStream()));

    String line = null;

    while ((output.readLine()) != null) {
        System.out.println(line);
    }

    int exitValue = process.waitFor();
    System.out.println("Command exited with exit value: " + exitValue);

    process.destroy();
    System.out.println("destroyed");
} catch (IOException e) {
    e.printStackTrace();
} catch (InterruptedException e) {
    e.printStackTrace();
}

And I get this for an output:

(18 lines of just "null")
Command exited with exit value: 0
destroyed

Any ideas?

Answer 1

You never set your line variable that you are using to write to the console.

Replace

while ((output.readLine()) != null) {

with

while ((line = output.readLine()) != null) {