Indicates how to change the blocked signals; possible values are <command>SIG_BLOCK=0</command> (for blocking signals), <command>SIG_UNBLOCK=1</command> (for unblocking signals), and <command>SIG_SETMASK=2</command> for setting the signal mask.

The old address of the signal set (<command>sigset_t</command>)

The actual value to be set for <command>sigset_t</command> <remark>(correct?)</remark>

The address of the signal set (<command>sigset_t</command>) to be implemented