Signals


A signal is an asynchronous event
A process sends it using kill(2) and sigqueue(2)
A process catches it using signal(2) and sigaction(2)
It doesn't convey any information (unless extensions are used)

Signal(7) describes the signals
SIGTERM is control-C
SIGCHLD reports a child terminated
SIGSTOP blocks the process (control-Z)
SIGCONT resurrects a blocked process
SIGUSR1, SIGUSR2 are reserved for the user (often to {in,de}crease debug)
SIGIO  reports asynchronous input
SIGWINCH reports a text-terminal size change