title: My child process cannot receive the last value from parent process using Pipe
body: <p>in my program, child process should receive some value from keyboard, and send to parent process. Parent process should calculate the sum and return to child process. My program is shown below:</p>
  
  <blockquote>
    <p>3 4 5
    -1 child(4753): Sending 3 to parent Parent(4751): Received 3 Parent(4751): Sending 3 back Parent(4751): Received 4 Parent(4751):
    Sending 7 back Parent(4751): Received 5 child(4753): Received 3
    Parent(4751): Sending 12 back Parent(4753): Received 4 Parent(4753):
    Sending 7 back Parent(4753): Received 5 Parent(4753): Sending 12 back</p>
  </blockquote>
  
  <p>From the result, the last step is  Parent send 12 back  but child cannot received 12 and show the total sum. 
  Therefore, anyone has some ideas why the result is not my expected and how to modify my code?</p>
  
  <p>Thanks in advance.</p>