1.\" Copyright (c) 1985, 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.\" 4. 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.\" @(#)siginterrupt.3 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD$ 30.\" 31.Dd June 4, 1993 32.Dt SIGINTERRUPT 3 33.Os 34.Sh NAME 35.Nm siginterrupt 36.Nd allow signals to interrupt system calls 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In signal.h 41.Ft int 42.Fn siginterrupt "int sig" "int flag" 43.Sh DESCRIPTION 44The 45.Fn siginterrupt 46function 47is used to change the system call restart 48behavior when a system call is interrupted by the specified signal. 49If the flag is false (0), then system calls will be restarted if 50they are interrupted by the specified signal 51and no data has been transferred yet. 52System call restart has been the default behavior since 53.Bx 4.2 , 54and is the default behaviour for 55.Xr signal 3 56on 57.Fx . 58.Pp 59If the flag is true (1), 60then restarting of system calls is disabled. 61If a system call is interrupted by the specified signal 62and no data has been transferred, 63the system call will return \-1 with the global variable 64.Va errno 65set to 66.Er EINTR . 67Interrupted system calls that have started transferring 68data will return the amount of data actually transferred. 69System call interrupt is the signal behavior found on 70.Bx 4.1 71and 72.At V 73systems. 74.Pp 75Note that the new 76.Bx 4.2 77signal handling semantics are not 78altered in any other way. 79Most notably, signal handlers always remain installed until 80explicitly changed by a subsequent 81.Xr sigaction 2 82call, and the signal mask operates as documented in 83.Xr sigaction 2 . 84Programs may switch between restartable and interruptible 85system call operation as often as desired in the execution of a program. 86.Pp 87Issuing a 88.Fn siginterrupt 3 89call during the execution of a signal handler will cause 90the new action to take place on the next signal to be caught. 91.Sh NOTES 92This library routine uses an extension of the 93.Xr sigaction 2 94system call that is not available in 95.Bx 4.2 , 96hence it should not be used if backward compatibility is needed. 97.Sh RETURN VALUES 98.Rv -std siginterrupt 99.Sh ERRORS 100The 101.Fn siginterrupt 102call fails if: 103.Bl -tag -width Er 104.It Bq Er EINVAL 105The 106.Fa sig 107argument 108is not a valid signal number. 109.El 110.Sh SEE ALSO 111.Xr sigaction 2 , 112.Xr sigblock 2 , 113.Xr sigpause 2 , 114.Xr sigsetmask 2 , 115.Xr signal 3 116.Sh HISTORY 117The 118.Fn siginterrupt 119function appeared in 120.Bx 4.3 . 121