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.\" $FreeBSD$ 34.\" 35.Dd June 4, 1993 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 has been the default behavior since 55.Bx 4.2 , 56and is the default behaviour for 57.Xr signal 3 58on 59.Tn FreeBSD . 60.Pp 61If the flag is true (1), 62then restarting of system calls is disabled. 63If a system call is interrupted by the specified signal 64and no data has been transferred, 65the system call will return \-1 with the global variable 66.Va errno 67set to 68.Dv EINTR . 69Interrupted system calls that have started transferring 70data will return the amount of data actually transferred. 71System call interrupt is the signal behavior found on 72.Bx 4.1 73and 74.At V 75systems. 76.Pp 77Note that the new 78.Bx 4.2 79signal handling semantics are not 80altered in any other way. 81Most notably, signal handlers always remain installed until 82explicitly changed by a subsequent 83.Xr sigaction 2 84call, and the signal mask operates as documented in 85.Xr sigaction 2 . 86Programs may switch between restartable and interruptible 87system call operation as often as desired in the execution of a program. 88.Pp 89Issuing a 90.Fn siginterrupt 3 91call during the execution of a signal handler will cause 92the new action to take place on the next signal to be caught. 93.Sh NOTES 94This library routine uses an extension of the 95.Xr sigaction 2 96system call that is not available in 97.Bx 4.2 , 98hence it should not be used if backward compatibility is needed. 99.Sh RETURN VALUES 100A 0 value indicates that the call succeeded. 101A \-1 value indicates that an invalid signal number has been supplied. 102.Sh SEE ALSO 103.Xr sigaction 2 , 104.Xr sigblock 2 , 105.Xr sigpause 2 , 106.Xr sigsetmask 2 , 107.Xr signal 3 108.Sh HISTORY 109The 110.Fn siginterrupt 111function appeared in 112.Bx 4.3 . 113