This session is a continuation of previous session in which we discussed signals on the shell. This session deals with different system calls to send signals to a process using kill(), raise(), abort(), pause(), alarm(), sleep(), usleep(), nanosleep() functions. Ignoring and handling signals using signal() system call. Avoiding race conditions using signal mask and sigprocmask() system call. Limitations of signal() system call. Ignoring and handling signals using sigaction() system call