This chapter and the next two chapters discuss signals. Although the fundamental concepts are simple, our discussion is quite lengthy, since there are many details to cover.
This chapter covers the following topics:
the various different signals and their purposes;
the circumstances in which the kernel may generate a signal for a process, and the system calls that one process may use to send a signal to another process;
how a process responds to a signal by default, and the means by which a process can change its response to a signal, in particular, through the use of a signal handler, a programmer-defined function that is automatically invoked on receipt of a signal;
the use of the process signal mask to block ...