1.\" Copyright (c) 1985, 1991 Regents of the University of California. 2.\" 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.\" from: @(#)siginterrupt.3 6.2 (Berkeley) 4/19/91 33.\" $Id: siginterrupt.3,v 1.2 1993/07/30 08:38:50 mycroft Exp $ 34.\" 35.Dd April 19, 1991 36.Dt SIGINTERRUPT 3 37.Os BSD 4.3 38.Sh NAME 39.Nm siginterrupt 40.Nd allow signals to interrupt system calls 41.Sh SYNOPSIS 42.Fd #include <signal.h> 43.Ft int 44.Fn siginterrupt "int sig" "int flag" 45.Sh DESCRIPTION 46The 47.Fn siginterrupt 48function 49is used to change the system call restart 50behavior when a system call is interrupted by the specified signal. 51If the flag is false (0), then system calls will be restarted if 52they are interrupted by the specified signal 53and no data has been transferred yet. 54System call restart is the default behavior on 55.Bx 4.2 . 56.Pp 57If the flag is true (1), 58then restarting of system calls is disabled. 59If a system call is interrupted by the specified signal 60and no data has been transferred, 61the system call will return \-1 with the global variable 62.Va errno 63set to 64.Dv EINTR . 65Interrupted system calls that have started transferring 66data will return the amount of data actually transferred. 67System call interrupt is the signal behavior found on 68.Bx 4.1 69and 70.At V 71systems. 72.Pp 73Note that the new 74.Bx 4.2 75signal handling semantics are not 76altered in any other way. 77Most notably, signal handlers always remain installed until 78explicitly changed by a subsequent 79.Xr sigaction 2 80call, and the signal mask operates as documented in 81.Xr sigaction 2 . 82Programs may switch between restartable and interruptible 83system call operation as often as desired in the execution of a program. 84.Pp 85Issuing a 86.Fn siginterrupt 3 87call during the execution of a signal handler will cause 88the new action to take place on the next signal to be caught. 89.Sh NOTES 90This library routine uses an extension of the 91.Xr sigaction 2 92system call that is not available in 93.Bx 4.2 , 94hence it should not be used if backward compatibility is needed. 95.Sh RETURN VALUES 96A 0 value indicates that the call succeeded. 97A \-1 value indicates that an invalid signal number has been supplied. 98.Sh SEE ALSO 99.Xr sigaction 2 , 100.Xr sigblock 2 , 101.Xr sigpause 2 , 102.Xr sigsetmask 2 . 103.Sh HISTORY 104The 105.Fn siginterrupt 106function appeared in 107.Bx 4.3 . 108