1.\"	$OpenBSD: siginterrupt.3,v 1.14 2013/06/05 03:39:22 tedu 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.Dd $Mdocdate: June 5 2013 $
31.Dt SIGINTERRUPT 3
32.Os
33.Sh NAME
34.Nm siginterrupt
35.Nd allow signals to interrupt system calls
36.Sh SYNOPSIS
37.In signal.h
38.Ft int
39.Fn siginterrupt "int sig" "int flag"
40.Sh DESCRIPTION
41The
42.Fn siginterrupt
43function is used to change the system call restart
44behavior when a system call is interrupted by the specified signal.
45If
46.Fa flag
47is false (0), system calls will be restarted if
48they are interrupted by the specified signal
49.Fa sig
50and no data has been transferred yet.
51System call restart is the default behavior on
52.Ox .
53.Pp
54If
55.Fa flag
56is true (1),
57the 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.Er 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
68systems prior to
69.Bx 4.2
70as well as most systems based upon
71.At V .
72.Pp
73Programs may switch between restartable and interruptible
74system call operation as often as desired in the execution of a program.
75Issuing a
76.Fn siginterrupt
77call during the execution of a signal handler will cause
78the new action to take place on the next signal to be caught.
79.Sh RETURN VALUES
80.Fn siginterrupt
81returns 0 on success or \-1 if an invalid signal number has been
82specified.
83.Sh SEE ALSO
84.Xr sigaction 2 ,
85.Xr sigprocmask 2 ,
86.Xr sigsuspend 2
87.Sh HISTORY
88The
89.Fn siginterrupt
90function appeared in
91.Bx 4.3 .
92