.\" Copyright (c) 1983 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"	@(#)sigprocmask.2	6.2 (Berkeley) 08/21/90
.\"
.TH SIGPROCMASK 2 ""
.UC 7
.SH NAME
sigprocmask \- manipulate current signal mask
.SH SYNOPSIS
.nf
.B #include <signal.h>

.B sigprocmask(how, set, oset);
.B int how;
.B sigset_t *set, *oset;

.B mask = sigmask(signum)
.SH DESCRIPTION
The
.I sigprocmask
function examines and/or the current signal mask (those signals
that are blocked from delivery).
Signals are blocked if they are members of the current signal mask set.
.PP
If
.I set
is not null, the action of
.I sigprocmask
depends on the value of the parameter
.IR how .
The signal mask is changed as a function of the specified
.I set
and the current mask.
The function is specified by
.I how
using one of the following values from <signal.h>:
.IP SIG_BLOCK \w'SIG_SETMASK\0\0'u
The new mask is the union of the current mask and the specified
.IR set .
.IP SIG_UNBLOCK \w'SIG_SETMASK\0\0'u
The new mask is the intersection of the current mask
and the complement of the specified
.IR set .
.IP SIG_SETMASK \w'SIG_SETMASK\0\0'u
The current mask is replaced by the specified
.IR set .
.PP
If
.I oset
is not null,
the previous value of the signal mask.
When
.I set
is null, this provides a way to examine the signal mask without changing it.
.PP
The system
quietly disallows SIGKILL or SIGSTOP to be blocked.
.SH "RETURN VALUE
A 0 value indicated that the call succeeded.  A \-1 return value
indicates an error occurred and
.I errno
is set to indicated the reason.
.SH ERRORS
The
.I sigprocmask
call will fail and the signal mask will be unchanged if one
of the following occurs:
.TP 15
[EINVAL]
.I how
has a value other than those listed here.
.SH "SEE ALSO"
kill(2), sigaction(2), sigsetops(2), sigsuspend(2)