1.\" $NetBSD: siginterrupt.3,v 1.9 2002/02/07 07:00:17 ross 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 39.Sh NAME 40.Nm siginterrupt 41.Nd allow signals to interrupt system calls 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include \*[Lt]signal.h\*[Gt] 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 is the default behavior on 58.Bx 4.2 . 59.Pp 60If the flag is true (1), 61then restarting of system calls is disabled. 62If a system call is interrupted by the specified signal 63and no data has been transferred, 64the system call will return \-1 with the global variable 65.Va errno 66set to 67.Dv EINTR . 68Interrupted system calls that have started transferring 69data will return the amount of data actually transferred. 70System call interrupt is the signal behavior found on 71.Bx 4.1 72and 73.At V 74systems. 75.Pp 76Note that the new 77.Bx 4.2 78signal handling semantics are not 79altered in any other way. 80Most notably, signal handlers always remain installed until 81explicitly changed by a subsequent 82.Xr sigaction 2 83call, and the signal mask operates as documented in 84.Xr sigaction 2 . 85Programs may switch between restartable and interruptible 86system call operation as often as desired in the execution of a program. 87.Pp 88Issuing a 89.Fn siginterrupt 3 90call during the execution of a signal handler will cause 91the new action to take place on the next signal to be caught. 92.Sh NOTES 93This library routine uses an extension of the 94.Xr sigaction 2 95system call that is not available in 96.Bx 4.2 , 97hence it should not be used if backward compatibility is needed. 98.Sh RETURN VALUES 99A 0 value indicates that the call succeeded. 100A \-1 value indicates that an invalid signal number has been supplied. 101.Sh SEE ALSO 102.Xr sigaction 2 , 103.Xr sigprocmask 2 , 104.Xr sigsuspend 2 105.Sh HISTORY 106The 107.Fn siginterrupt 108function appeared in 109.Bx 4.3 . 110