Pipes and Signals

Quick Reference

Pipe pattern:

int fd[2];
pipe(fd);           // fd[0] = read end, fd[1] = write end

if (fork() == 0) {  // Child (writer)
    close(fd[0]);   // Close unused read end
    write(fd[1], data, len);
    close(fd[1]);
    exit(0);
} else {            // Parent (reader)
    close(fd[1]);   // Close unused write end
    read(fd[0], buf, sizeof(buf));
    close(fd[0]);
    wait(NULL);
}

Common signals:

Common Pitfalls

• Pipe before fork – The pipe must be created before fork(). Otherwise parent and child have separate pipes.
• Close unused ends – Failing to close causes deadlocks (read blocks forever waiting for EOF).
• Zombie processes – Always wait() for children. Use WNOHANG for non-blocking checks.
• Signal handler safety – Only call async-signal-safe functions (write, _exit) inside handlers. printf is NOT safe.