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.\" 34.Dd June 4, 1993 35.Dt SIGINTERRUPT 3 36.Os BSD 4.3 37.Sh NAME 38.Nm siginterrupt 39.Nd allow signals to interrupt system calls 40.Sh SYNOPSIS 41.Fd #include <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 has been the default behavior since 54.Bx 4.2 , 55and is the default behaviour for 56.Xr signal 3 57on 58.Tn FreeBSD . 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 sigblock 2 , 104.Xr signal 3 , 105.Xr sigpause 2 , 106.Xr sigsetmask 2 . 107.Sh HISTORY 108The 109.Fn siginterrupt 110function appeared in 111.Bx 4.3 . 112