signal---specify handler subroutine for a signal
#include <signal.h> void ( * signal(int sig, void(*func)(int)) )(int); void ( * _signal_r(void *reent, int sig, void(*func)(int)) )(int); int raise (int sig); int _raise_r (void *reent, int sig);
signal, raise provide a simple signal/raise implementation for embedded
signal allows you to request changed treatment for a particular
signal sig. You can use one of the predefined macros
(select system default handling) or
SIG_IGN (ignore this signal)
as the value of func; otherwise, func is a function pointer
that identifies a subroutine in your program as the handler for this signal.
Some of the execution environment for signal handlers is
unpredictable; notably, the only library function required to work
correctly from within a signal handler is
signal itself, and
only when used to redefine the handler for the current signal value.
Static storage is likewise unreliable for signal handlers, with one
exception: if you declare a static storage location as `
sig_atomic_t', then you may use that location in a signal handler to
store signal values.
If your signal handler terminates using
return (or implicit
return), your program's execution continues at the point
where it was when the signal was raised (whether by your program
itself, or by an external event). Signal handlers can also
use functions such as
abort to avoid returning.
raise sends the signal sig to the executing program. It returns zero if
successful, non-zero if unsuccessful.
The alternate functions
_signal_r, _raise_r are the reentrant versions.
The extra argument reent is a pointer to a reentrancy structure.
If your request for a signal handler cannot be honored, the result is
SIG_ERR; a specific error number is also recorded in
Otherwise, the result is the previous handler (a function pointer or one of the predefined macros).
ANSI C requires
No supporting OS subroutines are required to link with
it will not have any useful effects, except for software generated signals,
without an operating system that can actually raise exceptions.
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