Manual Section... (3) - page: sigrelse NAMEsigset, sighold,
sigrelse, sigignore - System V signal API SYNOPSIS#define
_XOPEN_SOURCE 500 typedef void (*sighandler_t)(int);
sighandler_t sigset(int sig, sighandler_t disp); int sighold(int
sig); int sigrelse(int sig); DESCRIPTIONThese functions are
provided in glibc as a compatibility interface for programs that
make use of the historical System V signal API. This API is
obsolete: new applications should use the POSIX signal API
(sigaction(2), sigprocmask(2), etc.) The sigset() function
modifies the disposition of the signal sig. The disp argument
can be the address of a signal handler function, or one of the
following constants: - Reset the disposition of sig to the
default. - Ignore sig. - Add sig to the process's signal mask,
but leave the disposition of sig unchanged. If disp specifies
the address of a signal handler, then sig is added to the
process's signal mask during execution of the handler. If disp
was specified as a value other than SIG_HOLD, then sig