struct sigaction (see Advanced Signal Handling); it is used to specify signal actions to the sigvec function. It contains the following members:
sighandler_t sv_handler
int sv_mask
int sv_flags sv_onstack .
These symbolic constants can be used to provide values for the sv_flags field of a sigvec structure. This field is a bit mask value, so you bitwise-OR the flags of interest to you together.
sv_flags field of a sigvec structure, it means to use the signal stack when delivering the signal.
sv_flags field of a sigvec structure, it means that system calls interrupted by this kind of signal should not be restarted if the handler returns; instead, the system calls should return with a EINTR error status. See Interrupted Primitives.
sv_flags field of a sigvec structure, it means to reset the action for the signal back to SIG_DFL when the signal is received.
sigaction (see Advanced Signal Handling); it installs the action action for the signal signum, returning information about the previous action in effect for that signal in old-action.
EINTR . See Interrupted Primitives.