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1.9 The Standard Headers: <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 behaviour 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

Returns

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 behaviour; 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.

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int raise(int sig);

raise send the signal sig to the program.

Returns

Non-zero if unsuccessful.

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