C++ Programming/Code/Standard C Library/Functions/signal
void (*signal( int sig, void (*handler)(int)) )(int)
The signal() function takes two parameters - the first is the signal identifier, and the second is a function pointer to a signal handler that takes one parameter. The return value of signal is a function pointer to the previous handler (or SIG_ERR if there was an error changing the signal handler).
By default, most raised signals are handled either by the handlers SIG_DFL (which is the default signal handler that usually shuts down the program), or SIG_IGN (which ignores the signal and continues program execution.)
When you specify a custom handler and the signal is raised, the signal handler reverts to the default.
While the signal handlers are superseded by throw and catch, some systems may still require you to use these functions to handle some important events. For example, the signal SIGTERM on Unix-based systems indicates that the program should terminate soon.
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