Sending data to stdin of another process through linux terminal

Question

I've been trying to send data to stdin of a running process. Here is what I do:

1. In a terminal I've started a c++ program that simply reads a string and prints it. Code excerpt:

   while (true) {
       cin >> s;
       cout << "I've just read " << s << endl;
   }
   

2. I get the PID of the running program

3. I go to /proc/PID/fd/
4. I execute echo text > 0

Result: text appears in the terminal where the program is run. Note, not I've just read text, but simply text. What am I doing wrong and what should I do to get this thing to print 'I've just read text'?

Answer 1

When you're starting your C++ program you need to make sure its input comes from a pipe but not from a terminal. You may use cat | myapp to do that. Once it's running you may use PID of your application for echo text > /proc/PID/fd/0