How to get live java output from console application

Question

I run code attached below but it gives output only after the command has completed in the String response. I want the console window activated during the running of command and get output of the command.

String command = "src\\youtube-dl"
                + " --max-downloads " + maxdown.getText()
                + " --retries " + noofretry.getText()
                + " --write-all-thumbnails" + sub.getText() 
                + " " + url.getText();

String response = "";
try {   
  Process p = Runtime.getRuntime().exec(command);
  InputStream in = p.getInputStream();
  ByteArrayOutputStream baos = new ByteArrayOutputStream();

  int c = -1;
  while((c = in.read()) != -1) {
    baos.write(c);
    System.out.flush();
    response = response + new String(baos.toByteArray());
    System.out.println(response);
  }         

} catch (Exception e) {
  e.printStackTrace();
}

You appear to be running youtube-dl directly, so this question has nothing to do with cmd.exe. The console window is not cmd. — Eryk Sun
– Eryk Sun, Commented Jun 23, 2017 at 15:21
There isn't anything you can easily do if you don't have access to the source code of youtube-dl and it uses full buffering when StandardOutput is a pipe. It will flush its buffer to the pipe either when its full (typically 4 KB) or at exit. The workarounds are complicated, such as DLL injection and API hooking or actively scraping a console screen buffer. — Eryk Sun
– Eryk Sun, Commented Jun 23, 2017 at 15:22

Pradeep · Accepted Answer · 2017-06-23 11:16:37Z

0

Please try using waitFor method until the response is flushed properly to the output stream

 Process p = null;
    try {
        p = p = r.exec(cmd2);
        p.getOutputStream().close(); // close stdin of child

        InputStream processStdOutput = p.getInputStream();
        Reader r = new InputStreamReader(processStdOutput);
        BufferedReader br = new BufferedReader(r);
        String line;
        while ((line = br.readLine()) != null) {
             //System.out.println(line); // the output is here
        }

        p.waitFor();
    }
    catch (InterruptedException e) {
            ... 
    }
    catch (IOException e){
            ...
    }
    finally{
        if (p != null)
            p.destroy();
    }

Ref:

Get output of cmd command from java code

answered Jun 23, 2017 at 11:16

Pradeep

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