NOTES
Prototypes for these functions are only available if _BSD_SOURCE is defined before the inclusion of any system header file. It is not possible to block SIGKILL or SIGSTOP - this restriction is silently imposed by the system.
"CONFORMING TO"
4.4BSD. These function calls appeared in BSD 4.3 and are deprecated. Use the POSIX signal facilities for new programs.
"SEE ALSO"
kill(2), sigprocmask(2), signal(7)