Task on pipe/FIFO

Task #

In this task, we will simulate the OPS Laboratory. The laboratory consists of n (3 <= n <= 20, the only program parameter) students and one teacher. Students solve a task divided into four stages, worth 3, 6, 7, and 5 points respectively. Each student has a skill level k (a random integer, 3 <= k <= 9), which determines their ability to solve the task.

Stages #

  1. Process Creation:

    • The main process (teacher) creates n child processes (students).
    • Each student prints their process ID and exits.

  2. Attendance Check:

    • Students communicate with the teacher through pipes.
    • A shared pipe allows students to write to the teacher, while the teacher communicates with each student through individual pipes.
    • The teacher takes attendance by sending Teacher: Is [PID] here? to each student and the standard output.
    • Students respond with Student [PID]: HERE through both the shared pipe and standard output.
    • After the attendance check, all processes exit.

  3. Task Stages:

    • After the attendance check, students begin the task by following these steps for each stage:

      1. Generate a random integer t in the range [100, 500].
      2. Wait t milliseconds.
      3. Generate a random integer q from [1, 20], representing their attempt score.
      4. Compute their total attempt score as k + q.
      5. Send their process ID and attempt score to the teacher.
      6. The teacher compares the attempt score against the stage difficulty (d), which is calculated as the stage’s base points plus a random integer from [1, 20].
      7. If k + q >= d, the student succeeds; otherwise, they fail. The information is sent back to the student.
      8. The teacher prints one of the following messages:
        • Teacher: Student [PID] finished stage [X] (on success).
        • Teacher: Student [PID] needs to fix stage [X] (on failure).
      9. If a student completes all four stages, they print Student [PID]: I NAILED IT! and exit.

    • The teacher waits for all students to finish. After all students exit, the teacher prints Teacher: IT'S FINALLY OVER! and exits.

  4. Time Limit:

    • The laboratory session may end if time runs out. This is handled using the alarm(2) function after attendance is checked.
    • When the SIGALRM signal is received, the teacher prints Teacher: END OF TIME!, stops grading students, and prints a summary table before releasing resources and exiting.
    • Each student detects that the teacher has left and prints Student [PID]: Oh no, I haven't finished stage [X]. I need more time. before exiting.

Example output #

./sop-lab 5
Student: 47807
Student: 47808
Student: 47809
Student: 47810
Teacher: 47806
Teacher: Is 47807 here?
Student 47807: HERE!
Teacher: Is 47808 here?
Student: 47811
Student 47808: HERE!
Teacher: Is 47809 here?
Student 47809: HERE!
Teacher: Is 47810 here?
Student 47810: HERE!
Teacher: Is 47811 here?
Student 47811: HERE!
Teacher: Student 47808 finished stage 1
Teacher: Student 47809 finished stage 1
Teacher: Student 47811 finished stage 1
Teacher: Student 47807 needs to fix stage 1
Teacher: Student 47810 finished stage 1
Teacher: Student 47809 finished stage 2
Teacher: Student 47807 finished stage 1
Teacher: Student 47808 needs to fix stage 2
Teacher: Student 47810 finished stage 2
Teacher: Student 47811 needs to fix stage 2
Teacher: Student 47807 needs to fix stage 2
Teacher: Student 47809 finished stage 3
Teacher: Student 47810 needs to fix stage 3
Teacher: Student 47808 needs to fix stage 2
Teacher: Student 47807 needs to fix stage 2
Teacher: Student 47809 needs to fix stage 4
Teacher: Student 47811 needs to fix stage 2
Teacher: Student 47807 needs to fix stage 2
Teacher: Student 47809 needs to fix stage 4
Teacher: Student 47807 finished stage 2
Teacher: Student 47811 needs to fix stage 2
Teacher: Student 47810 needs to fix stage 3
Teacher: Student 47808 needs to fix stage 2
Teacher: Student 47809 needs to fix stage 4
Teacher: Student 47807 finished stage 3
Teacher: Student 47811 finished stage 2
Teacher: Student 47810 needs to fix stage 3
Teacher: Student 47808 needs to fix stage 2
Student 47807: I NAILED IT!
Teacher: Student 47807 finished stage 4
Teacher: END OF TIME!
Teacher: 47807 - 21
Teacher: 47808 - 3
Teacher: 47809 - 16
Teacher: 47810 - 9
Teacher: 47811 - 9
Teacher: IT'S FINALLY OVER!
Student 47809: Oh no, I haven't finished stage 4. I need more time.
Student 47810: Oh no, I haven't finished stage 3. I need more time.
Student 47811: Oh no, I haven't finished stage 3. I need more time.
Student 47808: Oh no, I haven't finished stage 2. I need more time.