sigset()
A default action is provided for each kind of signal, such as terminate, stop, or ignore
For nearly all signal types, the default action can be changed using the signal() function. The exceptions are SIGKILL and SIGSTOP
Usage: signal(int sig, void (*disp)(int))
For each process, UNIX maintains a table of actions that should be performed for each kind of signal. The signal() function changes the table entry for the signal named as the first argument to the value provided as the second argument
The second argument can be SIG_IGN (ignore the signal), SIG_DFL (perform default action), or a pointer to a signal handler function