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.\" $FreeBSD$ 30.\" 31.Dd May 7, 2010 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.Fo sigprocmask 43.Fa "int how" 44.Fa "const sigset_t * restrict set" 45.Fa "sigset_t * restrict oset" 46.Fc 47.Sh DESCRIPTION 48The 49.Fn sigprocmask 50system call examines and/or changes the current signal mask (those signals 51that are blocked from delivery). 52Signals are blocked if they are members of the current signal mask set. 53.Pp 54If 55.Fa set 56is not null, the action of 57.Fn sigprocmask 58depends on the value of the 59.Fa how 60argument. 61The signal mask is changed as a function of the specified 62.Fa set 63and the current mask. 64The function is specified by 65.Fa how 66using one of the following values from 67.In signal.h : 68.Bl -tag -width SIG_UNBLOCK 69.It Dv SIG_BLOCK 70The new mask is the union of the current mask and the specified 71.Fa set . 72.It Dv SIG_UNBLOCK 73The new mask is the intersection of the current mask 74and the complement of the specified 75.Fa set . 76.It Dv SIG_SETMASK 77The current mask is replaced by the specified 78.Fa set . 79.El 80.Pp 81If 82.Fa oset 83is not null, it is set to 84the previous value of the signal mask. 85When 86.Fa set 87is null, 88the value of 89.Fa how 90is insignificant and the mask remains unset 91providing a way to examine the signal mask without modification. 92.Pp 93The system 94quietly disallows 95.Dv SIGKILL 96or 97.Dv SIGSTOP 98to be blocked. 99.Pp 100In threaded applications, 101.Xr pthread_sigmask 3 102must be used instead of 103.Fn sigprocmask . 104.Sh RETURN VALUES 105.Rv -std sigprocmask 106.Sh ERRORS 107The 108.Fn sigprocmask 109system call will fail and the signal mask will be unchanged if one 110of the following occurs: 111.Bl -tag -width Er 112.It Bq Er EINVAL 113The 114.Fa how 115argument 116has a value other than those listed here. 117.El 118.Sh SEE ALSO 119.Xr kill 2 , 120.Xr sigaction 2 , 121.Xr sigpending 2 , 122.Xr sigsuspend 2 , 123.Xr fpsetmask 3 , 124.Xr pthread_sigmask 3 , 125.Xr sigsetops 3 126.Sh STANDARDS 127The 128.Fn sigprocmask 129system call is expected to 130conform to 131.St -p1003.1-90 . 132