Java – how to check whether another (non-Java) process is running on Linux

Issue

I’m having some weird problems with this.

We are using Xvfb virtual desktop manager and want to make sure it’s running before I continue. Using pure shell, I could do this easily:

    ps -ef | grep Xvfb | grep -v grep

And that gives me exactly what I need, a single line containing information about the Xvfb proc. Next, I want to incorporate this into my Java program and parse the results and store the PID of the running Xvfb process. So I am trying this:

    String line;
    try {
      Process p = Runtime.getRuntime().exec("ps -ef | grep Xvfb | grep -v grep");
      BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
      while ((line = input.readLine()) != null)
      {
        System.out.println(line);
      }
    } catch (Exception err) {
      System.out.println(err);
    }

The bizarre thing is that if I use “ps -ef”, I get a huge list of processes dumped to my console when I run my app. But if I use | grep to narrow the list of processes returned, I get zero results. input.readLine() gets null every time.

I have also tried:

    ps -ef | grep Xvfb | grep -v grep | awk {'print $2'}

To just grab the process id. Also, no luck.

Has anyone else experienced this or know what I’m doing wrong?

Solution

You’re trying to use the “|” which is a pipe function that is particular to the shell, therefore you cannot do it in the java process. You could just try getting the process ID by using pidof Xvfb.

Answered By – Max

This Answer collected from stackoverflow, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0

Leave a Reply

(*) Required, Your email will not be published