Thread: why is terminal not returning results to ide

hi i am trying to run a command in terminal the code is below if i run the command in terminal it works fine however when i run it from netbeans with code below nothing gets printed. however if i run a different command such as (ip addr) it works fine any ideas on why?

public static void a() throws IOException{
            ArrayList lister=new ArrayList();
            Runtime rt = Runtime.getRuntime();
            Process proc = rt.exec("ps -ef | grep firefox");// the command i am trying to run to get pid of application
            InputStream stderr = proc.getInputStream();
            InputStreamReader isr = new InputStreamReader(stderr);
            BufferedReader br = new BufferedReader(isr);
            String line;
            while ( (line = br.readLine()) != null){
                lister.add(line);
            }
            for(int y=0;y<lister.size();y++){
                System.out.println(lister.get(y));
            }
    }

Process proc = rt.exec(new String[] { "/bin/sh", "-c", "ps -ef | grep firefox" });

this solution worked thanks for replys