sigprocmask(2)                                               sigprocmask(2)

NAME
     sigprocmask - change or test signal mask

SYNOPSIS
     #include <signal.h>

     int sigprocmask(int how, const sigsett *set, const sigsett *oset);

DESCRIPTION
     The sigprocmask() function is used to examine and/or change the cal-
     ling process' signal mask. If the value is SIGBLOCK, the set pointed
     to by the argument set is added to the current signal mask. If the
     value is SIGUNBLOCK, the set pointed by the argument set is removed
     from the current signal mask. If the value is SIGSETMASK, the current
     signal mask is replaced by the set pointed to by the argument set. If
     the argument oset is not NULL, the previous mask is stored in the
     space pointed to by oset. If the value of the argument set is NULL,
     the value how is not significant and the process' signal mask is
     unchanged; thus, the call can be used to enquire about currently
     blocked signals.

     If there are any pending unblocked signals after the call to sigproc-
     mask(), at least one of those signals will be delivered before the
     call to sigprocmask() returns.

     It is not possible to block those signals that cannot be ignored [see
     sigaction(2)]; this restriction is silently imposed by the system.

     If any of the SIGFPE, SIGKILL or SIGSEGV signals are generated while
     they are blocked, the result is undefined, unless the signal was gen-
     erated by a call to kill() or raise().

     If sigprocmask() fails, the process' signal mask is not changed.

     sigprocmask() fails if any of the following are true:

     EINVAL   The value of the how argument is not equal to one of the
              defined values.

     EFAULT   set or oset points outside the process' allocated address
              space.

RESULT
     On success, sigprocmask() returns 0. On failure, it returns -1 and
     sets errno to indicate the error.

SEE ALSO
     sigaction(2), signal(2), sigsetops(3C), signal(5).







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