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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)siginterrupt.3 8.1 (Berkeley) 6/4/93 29.\" 30.Dd June 4, 1993 31.Dt SIGINTERRUPT 3 32.Os 33.Sh NAME 34.Nm siginterrupt 35.Nd allow signals to interrupt system calls 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In signal.h 40.Ft int 41.Fn siginterrupt "int sig" "int flag" 42.Sh DESCRIPTION 43The 44.Fn siginterrupt 45function 46is used to change the system call restart 47behavior when a system call is interrupted by the specified signal. 48If the flag is false (0), then system calls will be restarted if 49they are interrupted by the specified signal 50and no data has been transferred yet. 51System call restart has been the default behavior since 52.Bx 4.2 , 53and is the default behaviour for 54.Xr signal 3 55on 56.Fx . 57.Pp 58If the flag is true (1), 59then restarting of system calls is disabled. 60If a system call is interrupted by the specified signal 61and no data has been transferred, 62the system call will return \-1 with the global variable 63.Va errno 64set to 65.Er EINTR . 66Interrupted system calls that have started transferring 67data will return the amount of data actually transferred. 68System call interrupt is the signal behavior found on 69.Bx 4.1 70and 71.At V 72systems. 73.Pp 74Note that the new 75.Bx 4.2 76signal handling semantics are not 77altered in any other way. 78Most notably, signal handlers always remain installed until 79explicitly changed by a subsequent 80.Xr sigaction 2 81call, and the signal mask operates as documented in 82.Xr sigaction 2 . 83Programs may switch between restartable and interruptible 84system call operation as often as desired in the execution of a program. 85.Pp 86Issuing a 87.Fn siginterrupt 3 88call during the execution of a signal handler will cause 89the new action to take place on the next signal to be caught. 90.Sh NOTES 91This library routine uses an extension of the 92.Xr sigaction 2 93system call that is not available in 94.Bx 4.2 , 95hence it should not be used if backward compatibility is needed. 96.Sh RETURN VALUES 97.Rv -std siginterrupt 98.Sh ERRORS 99The 100.Fn siginterrupt 101call fails if: 102.Bl -tag -width Er 103.It Bq Er EINVAL 104The 105.Fa sig 106argument 107is not a valid signal number. 108.El 109.Sh SEE ALSO 110.Xr sigaction 2 , 111.Xr sigprocmask 2 , 112.Xr sigsuspend 2 , 113.Xr signal 3 114.Sh HISTORY 115The 116.Fn siginterrupt 117function appeared in 118.Bx 4.3 . 119