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.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)siginterrupt.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD: src/lib/libc/gen/siginterrupt.3,v 1.6.2.4 2001/12/14 18:33:51 ru Exp $ 34.\" $DragonFly: src/lib/libc/gen/siginterrupt.3,v 1.3 2004/03/11 12:28:50 hmp Exp $ 35.\" 36.Dd June 4, 1993 37.Dt SIGINTERRUPT 3 38.Os 39.Sh NAME 40.Nm siginterrupt 41.Nd allow signals to interrupt system calls 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In signal.h 46.Ft int 47.Fn siginterrupt "int sig" "int flag" 48.Sh DESCRIPTION 49The 50.Fn siginterrupt 51function 52is used to change the system call restart 53behavior when a system call is interrupted by the specified signal. 54If the flag is false (0), then system calls will be restarted if 55they are interrupted by the specified signal 56and no data has been transferred yet. 57System call restart has been the default behavior since 58.Bx 4.2 , 59and is the default behaviour for 60.Xr signal 3 61on 62.Dx . 63.Pp 64If the flag is true (1), 65then restarting of system calls is disabled. 66If a system call is interrupted by the specified signal 67and no data has been transferred, 68the system call will return \-1 with the global variable 69.Va errno 70set to 71.Er EINTR . 72Interrupted system calls that have started transferring 73data will return the amount of data actually transferred. 74System call interrupt is the signal behavior found on 75.Bx 4.1 76and 77.At V 78systems. 79.Pp 80Note that the new 81.Bx 4.2 82signal handling semantics are not 83altered in any other way. 84Most notably, signal handlers always remain installed until 85explicitly changed by a subsequent 86.Xr sigaction 2 87call, and the signal mask operates as documented in 88.Xr sigaction 2 . 89Programs may switch between restartable and interruptible 90system call operation as often as desired in the execution of a program. 91.Pp 92Issuing a 93.Fn siginterrupt 3 94call during the execution of a signal handler will cause 95the new action to take place on the next signal to be caught. 96.Sh NOTES 97This library routine uses an extension of the 98.Xr sigaction 2 99system call that is not available in 100.Bx 4.2 , 101hence it should not be used if backward compatibility is needed. 102.Sh RETURN VALUES 103.Rv -std siginterrupt 104.Sh ERRORS 105The 106.Fn siginterrupt 107call fails if: 108.Bl -tag -width Er 109.It Bq Er EINVAL 110.Fa sig 111is not a valid signal number. 112.El 113.Sh SEE ALSO 114.Xr sigaction 2 , 115.Xr sigblock 2 , 116.Xr sigpause 2 , 117.Xr sigsetmask 2 , 118.Xr signal 3 119.Sh HISTORY 120The 121.Fn siginterrupt 122function appeared in 123.Bx 4.3 . 124