C Pocket Reference

Signals

The operating system can send processes a signal when an exceptional situation occurs. This may happen in the event of a severe fault, such as a memory addressing error for example, or when a hardware interrupt occurs. Signals can also be triggered by the user at the console, however, or by the program itself, using the function raise() . Functions and macros for dealing with signals are declared in the header file signal.h .

Each type of signal is assigned a constant signal number and identified by a macro name. These include the signals listed in Table 1-41.

Table 1-41. Macros for signals in signal.h

Signal number	Meaning
SIGABRT	Abort: abnormal program termination, as caused by the abort() function
SIGFPE	Floating point exception: caused by an overflow, division by 0, or other FPU or emulation errors
SIGILL	Illegal instruction: an invalid instruction was encountered in the machine code
SIGINT	Interrupt: the break key (e. g., Ctrl-C) was pressed
SIGSEGV	Segmentation violation: illegal memory access
SIGTERM	Terminate: a request to terminate the program (in Unix, the standard signal sent by the kill command)

Other signals may be defined depending on the operating system.

int raise( int sig );

Sends the signal sig to the program which called the function.

void ( *signal( int sig, void ( *func )( int )) )( int );

Specifies how the program responds to a signal with the number sig. The second argument, func, identifies the signal handler. This ...