SIGBLOCK(2)                      System Calls                      SIGBLOCK(2)




NAME

       sigblock, sigmask - temporarily block signals


SYNOPSIS

       #include <signal.h>

       long sigblock(long mask);
       #define sigmask(signum)


DESCRIPTION

       sigblock  is  used  to temporarily block the reception of signals.  The
       input parameter mask is a bit vector that specifies which  signals  are
       to  be  blocked;  a 1 in bit n will block signal n+1.  The mask is bit-
       wise-or'd with the current signal mask to create the new signal mask.

       sigmask is a macro that can be  used  to  calculate  signal  masks  for
       sigsetmask.   It  takes a signal number signum, as listed in signal(2),
       as an argument and returns a mask corresponding to that signal.

       If a signal is sent to a process but is blocked, the event is  recorded
       for  later  release by sigsetmask(2).  blocked signals are not stacked;
       further occurrences of a blocked signal  will  overwrite  any  previous
       pending signal of the same signum.

       It  is  not  possible  to  block  SIGKILL,  SIGCONT,  or SIGSTOP.  This
       restriction is silently enforced by the kernel.


RETURN VALUE

       The previous value of the signal mask is returned.


SEE ALSO

       kill(2), sigsetmask(2), signal(2)



GNO                             19 January 1997                    SIGBLOCK(2)

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