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	1	.\" $NetBSD: sigprocmask.2,v 1.6 1995/02/27 12:37:33 cgd Exp $
	2	.\"
	3	.\" Copyright (c) 1983, 1991, 1993
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)sigprocmask.2 8.1 (Berkeley) 6/4/93
	35	.\"
	36	.Dd June 4, 1993
	37	.Dt SIGPROCMASK 2
	38	.Os
	39	.Sh NAME
	40	.Nm sigprocmask
	41	.Nd manipulate current signal mask
	42	.Sh SYNOPSIS
	43	.Fd #include <signal.h>
	44	.Ft int
	45	.Fo sigprocmask
	46	.Fa "int how"
	47	.Fa "const sigset_t *restrict set"
	48	.Fa "sigset_t *restrict oset"
	49	.Fc
	50	.Sh DESCRIPTION
	51	The
	52	.Fn sigprocmask
	53	function examines and/or changes the current signal mask
	54	(those signals that are blocked from delivery).
	55	Signals are blocked if they are members of the current signal mask set.
	56	.Pp
	57	If
	58	.Fa set
	59	is not null, the action of
	60	.Fn sigprocmask
	61	depends on the value of the parameter
	62	.Fa how .
	63	The signal mask is changed as a function of the specified
	64	.Fa set
	65	and the current mask.
	66	The function is specified by
	67	.Fa how
	68	using one of the following values from
	69	.Aq Pa signal.h :
	70	.Bl -tag -width SIG_UNBLOCK
	71	.It Dv SIG_BLOCK
	72	The new mask is the union of the current mask and the specified
	73	.Fa set .
	74	.It Dv SIG_UNBLOCK
	75	The new mask is the intersection of the current mask
	76	and the complement of the specified
	77	.Fa set .
	78	.It Dv SIG_SETMASK
	79	The current mask is replaced by the specified
	80	.Fa set .
	81	.El
	82	.Pp
	83	If
	84	.Fa oset
	85	is not null, it is set to
	86	the previous value of the signal mask.
	87	When
	88	.Fa set
	89	is null,
	90	the value of
	91	.Ar how
	92	is insignificant and the mask remains unset
	93	providing a way to examine the signal mask without modification.
	94	.Pp
	95	The system
	96	quietly disallows
	97	.Dv SIGKILL
	98	or
	99	.Dv SIGSTOP
	100	to be blocked.
	101	.Sh RETURN VALUES
	102	A 0 value indicated that the call succeeded. A -1 return value
	103	indicates an error occurred and
	104	.Va errno
	105	is set to indicated the reason.
	106	.Sh ERRORS
	107	The
	108	.Fn sigprocmask
	109	call will fail and the signal mask will be unchanged if one
	110	of the following occurs:
	111	.Bl -tag -width Er
	112	.\" ===========
	113	.It Bq Er EINVAL
	114	.Fa how
	115	has a value other than those listed here.
	116	.El
	117	.Sh SEE ALSO
	118	.Xr kill 2 ,
	119	.Xr sigaction 2 ,
	120	.Xr sigsuspend 2 ,
	121	.Xr sigsetops 3
	122	.Sh STANDARDS
	123	The
	124	.Fn sigprocmask
	125	function call is expected to
	126	conform to
	127	.St -p1003.1-88 .