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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
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	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
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	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	.Fn sigprocmask "int how" "const sigset_t set" "sigset_t oset"
	46	.Sh DESCRIPTION
	47	The
	48	.Fn sigprocmask
	49	function examines and/or changes the current signal mask (those signals
	50	that are blocked from delivery).
	51	Signals are blocked if they are members of the current signal mask set.
	52	.Pp
	53	If
	54	.Fa set
	55	is not null, the action of
	56	.Fn sigprocmask
	57	depends on the value of the parameter
	58	.Fa how .
	59	The signal mask is changed as a function of the specified
	60	.Fa set
	61	and the current mask.
	62	The function is specified by
	63	.Fa how
	64	using one of the following values from
	65	.Aq Pa signal.h :
	66	.Bl -tag -width SIG_UNBLOCK
	67	.It Dv SIG_BLOCK
	68	The new mask is the union of the current mask and the specified
	69	.Fa set .
	70	.It Dv SIG_UNBLOCK
	71	The new mask is the intersection of the current mask
	72	and the complement of the specified
	73	.Fa set .
	74	.It Dv SIG_SETMASK
	75	The current mask is replaced by the specified
	76	.Fa set .
	77	.El
	78	.Pp
	79	If
	80	.Fa oset
	81	is not null, it is set to
	82	the previous value of the signal mask.
	83	When
	84	.Fa set
	85	is null,
	86	the value of
	87	.Ar how
	88	is insignificant and the mask remains unset
	89	providing a way to examine the signal mask without modification.
	90	.Pp
	91	The system
	92	quietly disallows
	93	.Dv SIGKILL
	94	or
	95	.Dv SIGSTOP
	96	to be blocked.
	97	.Sh RETURN VALUES
	98	A 0 value indicated that the call succeeded. A -1 return value
	99	indicates an error occurred and
	100	.Va errno
	101	is set to indicated the reason.
	102	.Sh ERRORS
	103	The
	104	.Fn sigprocmask
	105	call will fail and the signal mask will be unchanged if one
	106	of the following occurs:
	107	.Bl -tag -width Er
	108	.It Bq Er EINVAL
	109	.Fa how
	110	has a value other than those listed here.
	111	.El
	112	.Sh SEE ALSO
	113	.Xr kill 2 ,
	114	.Xr sigaction 2 ,
	115	.Xr sigsetops 3 ,
	116	.Xr sigsuspend 2
	117	.Sh STANDARDS
	118	The
	119	.Fn sigprocmask
	120	function call is expected to
	121	conform to
	122	.St -p1003.1-88 .