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@(#)sigprocmask.2 8.1 (Berkeley) 6/4/93
$FreeBSD: head/lib/libc/sys/sigprocmask.2 59954 2000-05-04 13:09:25Z phantom $
.Dd June 4, 1993 .Dt SIGPROCMASK 2 .Os .Sh NAME .Nm sigprocmask .Nd manipulate current signal mask .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include <signal.h> .Ft int .Fn sigprocmask "int how" "const sigset_t *set" "sigset_t *oset" .Sh DESCRIPTION The .Fn sigprocmask function examines and/or changes the current signal mask (those signals that are blocked from delivery). Signals are blocked if they are members of the current signal mask set.
p If .Fa set is not null, the action of .Fn sigprocmask depends on the value of the parameter .Fa how . The signal mask is changed as a function of the specified .Fa set and the current mask. The function is specified by .Fa how using one of the following values from .Aq Pa signal.h : l -tag -width SIG_UNBLOCK t Dv SIG_BLOCK The new mask is the union of the current mask and the specified .Fa set . t Dv SIG_UNBLOCK The new mask is the intersection of the current mask and the complement of the specified .Fa set . t Dv SIG_SETMASK The current mask is replaced by the specified .Fa set . .El
p If .Fa oset is not null, it is set to the previous value of the signal mask. When .Fa set is null, the value of .Ar how is insignificant and the mask remains unset providing a way to examine the signal mask without modification.
p The system quietly disallows .Dv SIGKILL or .Dv SIGSTOP to be blocked. .Sh RETURN VALUES A 0 value indicated that the call succeeded. A -1 return value indicates an error occurred and .Va errno is set to indicated the reason. .Sh ERRORS The .Fn sigprocmask call will fail and the signal mask will be unchanged if one of the following occurs: l -tag -width Er t Bq Er EINVAL .Fa how has a value other than those listed here. .Sh SEE ALSO .Xr kill 2 , .Xr sigaction 2 , .Xr sigsuspend 2 , .Xr fpsetmask 3 , .Xr sigsetops 3 .Sh STANDARDS The .Fn sigprocmask function call is expected to conform to .St -p1003.1-90 .