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B.9 Signals: <signal.h>
The header <signal.h> provides facilities for handling exceptional conditions that arise during execution, such as an interrupt signal from an external source or an error in execution.
void (*signal(int sig, void (*handler)(int)))(int)
signal determines how subsequent signals will be handled. If handler is SIG_DFL, the implementation-defined default behavior is used, if it is SIG_IGN, the signal is ignored; otherwise, the function pointed to by handler will be called, with the argument of the type of signal. Valid signals include
SIGABRT abnormal termination, e.g., from abort SIGFPE arithmetic error, e.g., zero divide or overflow SIGILL illegal function image, e.g., illegal instruction SIGINT interactive attention, e.g., interrupt SIGSEGV illegal storage access, e.g., access outside memory limits SIGTERM termination request sent to this program
signal returns the previous value of handler for the specific signal, or SIG_ERR if an error occurs.
When a signal sig subsequently occurs, the signal is restored to its default behavior; then the signal-handler function is called, as if by (*handler)(sig). If the handler returns, execution will resume where it was when the signal occurred.
The initial state of signals is implementation-defined.
int raise(int sig)
raise sends the signal sig to the program; it returns non-zero if unsuccessful.