1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)sigprocmask.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/sys/sigprocmask.2,v 1.8.2.5 2001/12/14 18:34:01 ru Exp $ 30.\" 31.Dd February 22, 2018 32.Dt SIGPROCMASK 2 33.Os 34.Sh NAME 35.Nm sigprocmask 36.Nd manipulate current signal mask 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In signal.h 41.Ft int 42.Fn sigprocmask "int how" "const sigset_t * restrict set" "sigset_t * restrict oset" 43.Sh DESCRIPTION 44The 45.Fn sigprocmask 46function examines and/or changes the current signal mask (those signals 47that are blocked from delivery). 48Signals are blocked if they are members of the current signal mask set. 49.Pp 50If 51.Fa set 52is not null, the action of 53.Fn sigprocmask 54depends on the value of the parameter 55.Fa how . 56The signal mask is changed as a function of the specified 57.Fa set 58and the current mask. 59The function is specified by 60.Fa how 61using one of the following values from 62.In signal.h : 63.Bl -tag -width ".Dv SIG_UNBLOCK" 64.It Dv SIG_BLOCK 65The new mask is the union of the current mask and the specified 66.Fa set . 67.It Dv SIG_UNBLOCK 68The new mask is the intersection of the current mask 69and the complement of the specified 70.Fa set . 71.It Dv SIG_SETMASK 72The current mask is replaced by the specified 73.Fa set . 74.El 75.Pp 76If 77.Fa oset 78is not null, it is set to 79the previous value of the signal mask. 80When 81.Fa set 82is null, 83the value of 84.Ar how 85is insignificant and the mask remains unset 86providing a way to examine the signal mask without modification. 87.Pp 88The system 89quietly disallows 90.Dv SIGKILL 91or 92.Dv SIGSTOP 93to be blocked. 94.Sh RETURN VALUES 95.Rv -std sigprocmask 96.Sh ERRORS 97The 98.Fn sigprocmask 99call will fail and the signal mask will be unchanged if one 100of the following occurs: 101.Bl -tag -width Er 102.It Bq Er EINVAL 103.Fa how 104has a value other than those listed here. 105.El 106.Sh SEE ALSO 107.Xr kill 2 , 108.Xr sigaction 2 , 109.Xr sigsuspend 2 , 110.Xr fpsetmask 3 , 111.Xr sigsetops 3 112.Sh STANDARDS 113The 114.Fn sigprocmask 115function call is expected to 116conform to 117.St -p1003.1-90 . 118