sigblock, siggetmask, sigsetmask, sigmask - manipulate the
       signal mask


SYNOPSIS

       #include <signal.h>

       int sigblock(int mask);

       int siggetmask(void);

       int sigsetmask(int mask);

       int sigmask(int signum);


DESCRIPTION

       This interface is made obsolete by sigprocmask(2).

       The sigblock system call adds  the  signals  specified  in
       mask  to  the  set of signals currently being blocked from
       delivery.

       The sigsetmask system call replaces  the  set  of  blocked
       signals totally with a new set specified in mask.  Signals
       are blocked if the corresponding bit in mask is a 1.

       The current set of blocked signals can be  obtained  using
       siggetmask.

       The  sigmask macro is provided to construct the mask for a
       given signum.



RETURN VALUES

       siggetmask returns the current set of masked signals.

       sigsetmask and sigblock return the previous set of  masked
       signals.


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 pro­
       grams.

       kill(2), sigprocmask(2), signal(7)