Non-Blocking_Wait

Non-Blocking Wait for Child Processes

Implementing a non-blocking wait alternative to the wait system call. It handles terminated child processes asynchronously, prints their PID, exit status, and termination reason (signal or normal exit), and ensures that no zombie processes are created.

---

Compilation

To compile the program, use the following command:

gcc -o non_blocking_wait non_blocking_wait.c

---

Usage

Run the compiled program:

./non_blocking_wait

---

Program Description

1. Sets up a SIGCHLD handler:

   • The handler uses waitpid with the WNOHANG flag to reap terminated child processes without blocking the parent.
   • It prints the PID, exit status, and termination reason (signal or normal exit) for each child.

2. Launches child processes:

   • Three child processes are created using fork.
   • Each child sleeps for a different duration and then exits:
     • The first child raises a segmentation fault (SIGSEGV) to simulate a signal-induced termination.
     • The other two children exit normally with different exit codes.

3. Parent process continues execution:

   • The parent process continues executing its main loop (while (1) { sleep(1); }) while handling child terminations asynchronously.

---

Example Output

Parenting...
Child 11532 terminated by signal 11 (Segmentation fault)
Child 11533 terminated normally with exit status 11
Child 11534 terminated normally with exit status 12

Explanation of the Output

• Parenting...: The parent process continues executing its main loop after launching the child processes.
• Child 11532 terminated by signal 11 (Segmentation fault): The first child process was terminated by a segmentation fault (signal 11, SIGSEGV).
• Child 11533 terminated normally with exit status 11: The second child process exited normally with an exit status of 11.
• Child 11534 terminated normally with exit status 12: The third child process exited normally with an exit status of 12.

---

Key Features

• Non-blocking wait: Uses WNOHANG to avoid blocking the parent process.
• Zombie prevention: All terminated children are reaped promptly.
• Async-signal safety: Uses write for printing in the signal handler to avoid unsafe functions.
• Race condition avoidance: Blocks SIGCHLD during setup to prevent missed signals.

---

Reqs

• A C compiler (eg. gcc).
• A POSIX-compliant operating system (Linux, macOS, etc..).