1.\" $NetBSD: siginterrupt.3,v 1.4 1997/01/17 03:45:01 perry Exp $ 2.\" 3.\" Copyright (c) 1985, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)siginterrupt.3 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt SIGINTERRUPT 3 38.Os BSD 4.3 39.Sh NAME 40.Nm siginterrupt 41.Nd allow signals to interrupt system calls 42.Sh SYNOPSIS 43.Fd #include <signal.h> 44.Ft int 45.Fn siginterrupt "int sig" "int flag" 46.Sh DESCRIPTION 47The 48.Fn siginterrupt 49function 50is used to change the system call restart 51behavior when a system call is interrupted by the specified signal. 52If the flag is false (0), then system calls will be restarted if 53they are interrupted by the specified signal 54and no data has been transferred yet. 55System call restart is the default behavior on 56.Bx 4.2 . 57.Pp 58If the flag is true (1), 59then restarting of system calls is disabled. 60If a system call is interrupted by the specified signal 61and no data has been transferred, 62the system call will return \-1 with the global variable 63.Va errno 64set to 65.Dv EINTR . 66Interrupted system calls that have started transferring 67data will return the amount of data actually transferred. 68System call interrupt is the signal behavior found on 69.Bx 4.1 70and 71.At V 72systems. 73.Pp 74Note that the new 75.Bx 4.2 76signal handling semantics are not 77altered in any other way. 78Most notably, signal handlers always remain installed until 79explicitly changed by a subsequent 80.Xr sigaction 2 81call, and the signal mask operates as documented in 82.Xr sigaction 2 . 83Programs may switch between restartable and interruptible 84system call operation as often as desired in the execution of a program. 85.Pp 86Issuing a 87.Fn siginterrupt 3 88call during the execution of a signal handler will cause 89the new action to take place on the next signal to be caught. 90.Sh NOTES 91This library routine uses an extension of the 92.Xr sigaction 2 93system call that is not available in 94.Bx 4.2 , 95hence it should not be used if backward compatibility is needed. 96.Sh RETURN VALUES 97A 0 value indicates that the call succeeded. 98A \-1 value indicates that an invalid signal number has been supplied. 99.Sh SEE ALSO 100.Xr sigaction 2 , 101.Xr sigprocmask 2 , 102.Xr sigsuspend 2 . 103.Sh HISTORY 104The 105.Fn siginterrupt 106function appeared in 107.Bx 4.3 . 108