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.Dd February 19, 2011
.Dt PTHREAD_SIGMASK 3
.Os
.Sh NAME
.Nm pthread_sigmask
.Nd examine and/or change a thread's signal mask
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.In signal.h
.Ft int
.Fn pthread_sigmask "int how" "const sigset_t * restrict set" \
    "sigset_t * restrict oset"
.Sh DESCRIPTION
The
.Fn pthread_sigmask
function examines and/or changes the calling thread's signal mask.
.Pp
If
.Fa set
is not
.Dv NULL ,
it specifies a set of signals to be modified, and
.Fa how
specifies what to set the signal mask to:
.Bl -tag -width SIG_UNBLOCK
.It Dv SIG_BLOCK
Union of the current mask and
.Fa set .
.It Dv SIG_UNBLOCK
Intersection of the current mask and the complement of
.Fa set .
.It Dv SIG_SETMASK
.Fa set .
.El
.Pp
If
.Fa oset
is not NULL, the previous signal mask is stored in the location pointed to by
.Fa oset .
.Pp
.Dv SIGKILL
and
.Dv SIGSTOP
cannot be blocked, and will be silently ignored if included in the signal mask.
.Sh RETURN VALUES
If successful,
.Fn pthread_sigmask
returns 0.
Otherwise, an error is returned.
.Sh ERRORS
The
.Fn pthread_sigmask
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
.Fa how
is not one of the defined values.
.El
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr sigpending 2 ,
.Xr sigprocmask 2 ,
.Xr sigsuspend 2 ,
.Xr sigsetops 3
.Sh STANDARDS
The
.Fn pthread_sigmask
function conforms to
.St -p1003.1-96