1.\" $NetBSD: siginterrupt.3,v 1.11 2003/08/07 16:42:56 agc 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)siginterrupt.3 8.1 (Berkeley) 6/4/93 31.\" 32.Dd June 4, 1993 33.Dt SIGINTERRUPT 3 34.Os 35.Sh NAME 36.Nm siginterrupt 37.Nd allow signals to interrupt system calls 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In signal.h 42.Ft int 43.Fn siginterrupt "int sig" "int flag" 44.Sh DESCRIPTION 45The 46.Fn siginterrupt 47function 48is used to change the system call restart 49behavior when a system call is interrupted by the specified signal. 50If the flag is false (0), then system calls will be restarted if 51they are interrupted by the specified signal 52and no data has been transferred yet. 53System call restart is the default behavior on 54.Bx 4.2 . 55.Pp 56If the flag is true (1), 57then restarting of system calls is disabled. 58If a system call is interrupted by the specified signal 59and no data has been transferred, 60the system call will return \-1 with the global variable 61.Va errno 62set to 63.Dv EINTR . 64Interrupted system calls that have started transferring 65data will return the amount of data actually transferred. 66System call interrupt is the signal behavior found on 67.Bx 4.1 68and 69.At V 70systems. 71.Pp 72Note that the new 73.Bx 4.2 74signal handling semantics are not 75altered in any other way. 76Most notably, signal handlers always remain installed until 77explicitly changed by a subsequent 78.Xr sigaction 2 79call, and the signal mask operates as documented in 80.Xr sigaction 2 . 81Programs may switch between restartable and interruptible 82system call operation as often as desired in the execution of a program. 83.Pp 84Issuing a 85.Fn siginterrupt 3 86call during the execution of a signal handler will cause 87the new action to take place on the next signal to be caught. 88.Sh NOTES 89This library routine uses an extension of the 90.Xr sigaction 2 91system call that is not available in 92.Bx 4.2 , 93hence it should not be used if backward compatibility is needed. 94.Sh RETURN VALUES 95A 0 value indicates that the call succeeded. 96A \-1 value indicates that an invalid signal number has been supplied. 97.Sh SEE ALSO 98.Xr sigaction 2 , 99.Xr sigprocmask 2 , 100.Xr sigsuspend 2 101.Sh HISTORY 102The 103.Fn siginterrupt 104function appeared in 105.Bx 4.3 . 106