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Runtime.process.exec()

2 replies. Most recent reply: Mar 6, 2002 12:54 PM by Aarti Thorat

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Aarti Thorat

Posts: 3
Nickname: at
Registered: Mar, 2002

Runtime.process.exec()

Posted: Mar 5, 2002 5:12 PM

Hi,

I posted a question sometime ago, but didnt get an answer hence am posting my core confusion.

I wonder Runtime.exec() can deal with user interaction
in subprocess. For example, program A calls program B
through Runtime.exec(). Program B gives some output and
receives standard input. I understand how B's output is
redirected to A, but I have no idea how B's standard
input(terminal input) can be handled. When I tried this
type of program, I found out two processes just
wait(maybe blocked) forever.

hope to get some input,
thanks!

Re: Runtime.process.exec()

Posted: Mar 6, 2002 12:27 AM

Posted by: Bill Venners Posts: 2284 / Nickname: bv / Registered: Jan, 2002

Well I assume your program B is trying to read user input from the standard input? If so, the problem is that program B's stdin is also hooked up to A (the program that called B with Runtime.exec().) A can get ahold of B's stdin by invoking Process.getOutputStream(). Can you perhaps let A grab input from the user and then pass it to B?

Re: Runtime.process.exec()

Posted: Mar 6, 2002 12:54 PM

Posted by: Aarti Thorat Posts: 3 / Nickname: at / Registered: Mar, 2002

Thanks for the input.
I did try this but the process behaves a little strangely than I expected or probably I am making a mistake somewhere. Here's the piece of code which does this.

InputStream prin = process.getInputStream();
BufferedReader bin = new BufferedReader(new InputStreamReader(prin));
String temp = bin.readLine();
System.out.println("the process output" + temp);
System.out.println("its trying to hook the input for B from A ");
OutputStream prout = process.getOutputStream();
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(isr);
String s = br.readLine();
System.out.println("taken input ");
byte[] sb = s.getBytes();
prout.write(sb);
prout.flush();

this code is put in a loop till process completes execution.

While executing this code I found out that the program executing this code just blocks.

Hope to get some input from you again.
Thanks!
Aarti.

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