How to send EOF to spawned process....

Question

Folks,
On Linux, the list of disks can be obtained as follows:
# format < /dev/null
Without redirecting /dev/null to its input, command "format" requires you to enter a value or CTRL-C.
I am trying to run format as a process within my Java code:
ProcessBuilder pb = new ProcessBuilder(args)
Process p = pb.start();
OutputStream os = p.getOutputStream();
os.close(); // Hopefully, sends EOF
p.waitFor();
As you can see, I am closing the input to the process, hoping that this will send an EOF to the process. However, the output that I get is erratic. Sometimes, I see the output and sometimes I don't.
My guess is that either I am not doing the right thing or may be I am closing the stream even before any processing is done.
I would appreciate your help in understanding what needs to be done to simulate redirecting /dev/null to the process.
Thank you in advance for your help.
Regards,
Peter

Answer 1

Thank you baptos and EJP.
I tried to show only the relevant code snippet earlier. I am also processing the other two streams using StreamGobbler class. Here are more details:
ProecessBuilder pb = new ProcessBuilder(args);
Process p = pb.start();
if (simulateDevNull == true) {
OutputStream os = p.getOutputStream();
os.close();
stdOut = new StreamGobbler(p.getInputStream());
stdErr = new StreamGobbler(p.getrrorStream());
stdOut.start();
stdErr.start();
p.waitFor();
Class StreamGobbler is a thread based class that can be used to process the output and the error from the spawned process in a separate thread. You can find many references to StreamGobbler class on the net.
Regards,
Peter