Waiting for the end of the process

Question

I'm executing a command using the Runtime class and I have to wait until the end of the command to get the results. But, I don't want to sleep the thread for some undeterminated time. I'd like it just to wait until the command ends.
See in this code:
try
String result="";
Process p = Runtime.getRuntime().exec("sh"); //open a new shell
InputStream is = p.getInputStream();
OutputStream os = p.getOutputStream();
os.write("ifconfig -a | grep PROMISC -c\n".getBytes());
os.flush();
try {
Thread.currentThread().sleep(1000);
/*command should take some time to execute so wait for 10 secs .... I don't like this .... I would prefer waiting for the end the command ifconfig*/
catch (InterruptedException eIE) { }
while (is.available() > 0)
result = result + ( (char) is.read());
System.out.println(result);
catch (IOException e) {
System.out.println(e);

Answer 1

AFAIK you can only detect if the shell process has finished, as sub-processes of the shell are not visible to your Java program (without resorting to OS-specific syscalls).
You can write "exit" (or whatever terminates your shell) in the output stream as the last command - this will quit the shell as soon as all commands are finished, and that will be visible to your prog. Note that you should not run ANY of the shell commands in background then, as this could cause the shell to exit before the commands are finished (and, depending on the system, even signal the subprocesses).