1.\" Copyright (c) 1983, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)sigprocmask.2 6.4 (Berkeley) 07/23/91 7.\" 8.Dd 9.Dt SIGPROCMASK 2 10.Os 11.Sh NAME 12.Nm sigprocmask 13.Nd manipulate current signal mask 14.Sh SYNOPSIS 15.Fd #include <signal.h> 16.Ft int 17.Fn sigprocmask "int how" "const sigset_t *set" "sigset_t *oset" 18.Fn sigmask signum 19.Sh DESCRIPTION 20The 21.Fn sigprocmask 22function examines and/or changes the current signal mask (those signals 23that are blocked from delivery). 24Signals are blocked if they are members of the current signal mask set. 25.Pp 26If 27.Fa set 28is not null, the action of 29.Fn sigprocmask 30depends on the value of the parameter 31.Fa how . 32The signal mask is changed as a function of the specified 33.Fa set 34and the current mask. 35The function is specified by 36.Fa how 37using one of the following values from 38.Aq Pa signal.h : 39.Bl -tag -width SIG_UNBLOCK 40.It Dv SIG_BLOCK 41The new mask is the union of the current mask and the specified 42.Fa set . 43.It Dv SIG_UNBLOCK 44The new mask is the intersection of the current mask 45and the complement of the specified 46.Fa set . 47.It Dv SIG_SETMASK 48The current mask is replaced by the specified 49.Fa set . 50.El 51.Pp 52If 53.Fa oset 54is not null, it is set to 55the previous value of the signal mask. 56When 57.Fa set 58is null, 59the value of 60.Ar how 61is insignificant and the mask remains unset 62providing a way to examine the signal mask without modification. 63.Pp 64The system 65quietly disallows 66.Dv SIGKILL 67or 68.Dv SIGSTOP 69to be blocked. 70.Sh RETURN VALUES 71A 0 value indicated that the call succeeded. A -1 return value 72indicates an error occurred and 73.Va errno 74is set to indicated the reason. 75.Sh ERRORS 76The 77.Fn sigprocmask 78call will fail and the signal mask will be unchanged if one 79of the following occurs: 80.Bl -tag -width Bq Er EINVAL 81.It Bq Er EINVAL 82.Fa how 83has a value other than those listed here. 84.Sh SEE ALSO 85.Xr kill 2 , 86.Xr sigaction 2 , 87.Xr sigsetops 3 , 88.Xr sigsuspend 2 89.Sh STANDARDS 90The 91.Nm sigprocmask 92function call is expected to 93conform to 94.St -p1003.1-88 . 95