What is signal?
The signal package includes programs for manipulating signal handling from the command line.
The sigaction program blocks, unblocks, ignores, or sets default behavior for signals and then executes a program.
The sigalarm program sets an alarm and executes a program. It optionally forks to execute the program and delivers an arbitrary signal to the child when the alarm goes off.
The sigpause program blocks, unblocks, ignores, or catches signals and then pauses awaiting the arrival of an unblocked signal. Upon receipt of a caught signal it executes a program.