Notes on Signals in UNIX

• Pressing a key generates an interrupt and kernel has a keyboard interrupt handler module. The KB interrupt handler would send a signal to all processes associated with the terminal.
• Once a signal handler is called, it is deleted from memory. So we call it recursively.

    void handler()
    {
        signal(SIGINT, handler);
    }

• Common Signals to know:
  • SIGSYS: Incorrect usage of a system call
  • SIGCHLD
  • SIGALRM
• SIGALRM is also used in sleep() call. Sleep call is just waiting infinitely for a signal. To create such wait, pause() function is used.

Written with StackEdit.