Question

I am a novice when it comes to java. I wanted to read the stdout from a process started in java. I got the following code upon a google search:

    Runtime rt = Runtime.getRuntime();
    Process proc = rt.exec(args);
    BufferedReader br = new BufferedReader(
        new InputStreamReader(proc.getInputStream()));
    while(br.ready()){
            System.out.println(br.readLine());
    }

However, this code does not print the output that the process (say, ls) is supposed to produce (btw, I am on Linux, openJDK 1.6)

But if I change the while loop to:

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

it works as expected.

What is the problem with the previous code? According to what the java api doc said, I thought they were similar.

Answer 1

In the previous loop, you’re simply looping on the ready state, not reading any bytes from the stream.