Question

tail -f test.log

Above command will tail the log which runs the process behind the scenes. How can I kill that particular process ?

I can press “Ctrl-Z” on the shell but I am running that command using Java and need to kill that process.

Any help on this will be much appreciated.

thanks

Answer 1

When you start a subprocess with Java you get back a Process object corresponding to the running process. You can use destroy() method on the Process object to kill the running command.

So you’d start it with:

  Process p = Runtime.getRuntime().exec(new String[] {"tail","-f","test.log"});

and kill it with:

 p.destroy();

If you are just reading new lines added to a file, have you considered doing this natively in Java? Reading the file is pretty straightforward:

 try {
  BufferedReader input = new BufferedReader(new FileReader("tail.log"));

  while (true) {
    String line;

    while ((line = input.readLine()) != null) {
      //You'll probably want to do something other than println()
      System.out.println(line);
    }

    try {
      Thread.sleep(500);
    } catch (InterruptedException e) {
      break;
    }

  }

  input.close();
 }
 catch (IOException ioe) {
   //Handle this
 }

You’ll probably want to run this in another Thread. And unlike tail -f the above code doesn’t handle the file being rewritten from the beginning rather than appended to, but you could fix that.