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.\" 35.Dd June 4, 1993 36.Dt SIGINTERRUPT 3 37.Os 38.Sh NAME 39.Nm siginterrupt 40.Nd allow signals to interrupt system calls 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In signal.h 45.Ft int 46.Fn siginterrupt "int sig" "int flag" 47.Sh DESCRIPTION 48The 49.Fn siginterrupt 50function 51is used to change the system call restart 52behavior when a system call is interrupted by the specified signal. 53If the flag is false (0), then system calls will be restarted if 54they are interrupted by the specified signal 55and no data has been transferred yet. 56System call restart has been the default behavior since 57.Bx 4.2 , 58and is the default behaviour for 59.Xr signal 3 60on 61.Dx . 62.Pp 63If the flag is true (1), 64then restarting of system calls is disabled. 65If a system call is interrupted by the specified signal 66and no data has been transferred, 67the system call will return \-1 with the global variable 68.Va errno 69set to 70.Er EINTR . 71Interrupted system calls that have started transferring 72data will return the amount of data actually transferred. 73System call interrupt is the signal behavior found on 74.Bx 4.1 75and 76.At V 77systems. 78.Pp 79Note that the new 80.Bx 4.2 81signal handling semantics are not 82altered in any other way. 83Most notably, signal handlers always remain installed until 84explicitly changed by a subsequent 85.Xr sigaction 2 86call, and the signal mask operates as documented in 87.Xr sigaction 2 . 88Programs may switch between restartable and interruptible 89system call operation as often as desired in the execution of a program. 90.Pp 91Issuing a 92.Fn siginterrupt 3 93call during the execution of a signal handler will cause 94the new action to take place on the next signal to be caught. 95.Sh NOTES 96This library routine uses an extension of the 97.Xr sigaction 2 98system call that is not available in 99.Bx 4.2 , 100hence it should not be used if backward compatibility is needed. 101.Sh RETURN VALUES 102.Rv -std siginterrupt 103.Sh ERRORS 104The 105.Fn siginterrupt 106call fails if: 107.Bl -tag -width Er 108.It Bq Er EINVAL 109.Fa sig 110is not a valid signal number. 111.El 112.Sh SEE ALSO 113.Xr sigaction 2 , 114.Xr sigprocmask 2 , 115.Xr sigsuspend 2 , 116.Xr signal 3 117.Sh HISTORY 118The 119.Fn siginterrupt 120function appeared in 121.Bx 4.3 . 122