1.\" Copyright (c) 1983, 1991 The Regents of the University of California. 2.\" 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.\" $OpenBSD: sigblock.3,v 1.20 2017/08/01 15:38:02 schwarze Exp $ 29.\" 30.Dd $Mdocdate: August 1 2017 $ 31.Dt SIGBLOCK 3 32.Os 33.Sh NAME 34.Nm sigblock , 35.Nm sigmask 36.Nd block signals 37.Sh SYNOPSIS 38.In signal.h 39.Ft int 40.Fn sigblock "int mask" 41.Ft int 42.Fn sigmask "int signum" 43.Sh DESCRIPTION 44.Bf -symbolic 45This interface is made obsolete by 46.Ef 47.Xr sigprocmask 2 . 48.Pp 49.Fn sigblock 50adds the signals specified in 51.Fa mask 52to the set of signals currently 53being blocked from delivery. 54Signals are blocked if the 55corresponding bit in 56.Fa mask 57is a 1; the macro 58.Fn sigmask 59is provided to construct the mask for a given 60.Fa signum . 61.Pp 62It is not possible to block 63.Dv SIGKILL 64or 65.Dv SIGSTOP ; 66this restriction is silently 67imposed by the system. 68.Sh RETURN VALUES 69The previous set of masked signals is returned. 70.Sh EXAMPLES 71The following example utilizing 72.Fn sigblock : 73.Bd -literal -offset indent 74int omask; 75 76omask = sigblock(sigmask(SIGINT) | sigmask(SIGHUP)); 77.Ed 78.Pp 79Becomes: 80.Bd -literal -offset indent 81sigset_t set, oset; 82 83sigemptyset(&set); 84sigaddset(&set, SIGINT); 85sigaddset(&set, SIGHUP); 86sigprocmask(SIG_BLOCK, &set, &oset); 87.Ed 88.Pp 89Another use of 90.Fn sigblock 91is to get the current set of masked signals without changing what 92is actually blocked. 93Instead of: 94.Bd -literal -offset indent 95int set; 96 97set = sigblock(0); 98.Ed 99.Pp 100Use the following: 101.Bd -literal -offset indent 102sigset_t set; 103 104sigprocmask(SIG_BLOCK, NULL, &set); 105.Ed 106.Sh SEE ALSO 107.Xr kill 2 , 108.Xr sigaction 2 , 109.Xr sigprocmask 2 , 110.Xr sigaddset 3 , 111.Xr sigsetmask 3 112.Sh HISTORY 113A 114.Fn sigblock 115system call first appeared in 116.Bx 4.2 . 117In 118.Bx 4.3 Reno , 119it was reimplemented as a wrapper around 120.Xr sigprocmask 2 . 121The old system call was kept for compatibility until 122.Ox 4.9 . 123