What's the problem you're having with it? I think this was discussed on irc recently? This was the example I gave of using process_create which works:

    process_create('/bin/cat',
                   [], 
                   [stdout(pipe(Out)),stdin(pipe(In))]),  
    write(In, "hello"), nl(In), close(In), 
    read_line_to_codes(Out, Codes).