[apple/libc.git] / gen / siginterrupt.3

.\" Copyright (c) 1985, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)siginterrupt.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/gen/siginterrupt.3,v 1.14 2002/12/19 09:40:21 ru Exp $
.\"
.Dd June 4, 1993
.Dt SIGINTERRUPT 3
.Os
.Sh NAME
.Nm siginterrupt
.Nd allow signals to interrupt system calls
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In signal.h
.Ft int
.Fn siginterrupt "int sig" "int flag"
.Sh DESCRIPTION
The
.Fn siginterrupt
function
is used to change the system call restart
behavior when a system call is interrupted by the specified signal.
If the flag is false (0), then system calls will be restarted if
they are interrupted by the specified signal
and no data has been transferred yet.
System call restart has been the default behavior since
.Bx 4.2 ,
and is the default behaviour for
.Xr signal 3
on
.Fx .
.Pp
If the flag is true (1),
then restarting of system calls is disabled.
If a system call is interrupted by the specified signal
and no data has been transferred,
the system call will return \-1 with the global variable
.Va errno
set to
.Er EINTR .
Interrupted system calls that have started transferring
data will return the amount of data actually transferred.
System call interrupt is the signal behavior found on
.Bx 4.1
and
.At V
systems.
.Pp
Note that the new
.Bx 4.2
signal handling semantics are not
altered in any other way.
Most notably, signal handlers always remain installed until
explicitly changed by a subsequent
.Xr sigaction 2
call, and the signal mask operates as documented in
.Xr sigaction 2 .
Programs may switch between restartable and interruptible
system call operation as often as desired in the execution of a program.
.Pp
Issuing a
.Fn siginterrupt 3
call during the execution of a signal handler will cause
the new action to take place on the next signal to be caught.
.Sh NOTES
This library routine uses an extension of the
.Xr sigaction 2
system call that is not available in
.Bx 4.2 ;
hence, it should not be used if backward compatibility is needed.
.Sh RETURN VALUES
.Rv -std siginterrupt
.Sh ERRORS
The
.Fn siginterrupt
call fails if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa sig
argument
is not a valid signal number.
.El
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr sigblock 2 ,
.Xr sigpause 2 ,
.Xr sigsetmask 2 ,
.Xr signal 3
.Sh HISTORY
The
.Fn siginterrupt
function appeared in
.Bx 4.3 .
Commit	Line	Data
224c7076 A	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: src/lib/libc/gen/siginterrupt.3,v 1.14 2002/12/19 09:40:21 ru Exp $
	34	.\"
	35	.Dd June 4, 1993
	36	.Dt SIGINTERRUPT 3
	37	.Os
	38	.Sh NAME
	39	.Nm siginterrupt
	40	.Nd allow signals to interrupt system calls
	41	.Sh LIBRARY
	42	.Lb libc
	43	.Sh SYNOPSIS
	44	.In signal.h
	45	.Ft int
	46	.Fn siginterrupt "int sig" "int flag"
	47	.Sh DESCRIPTION
	48	The
	49	.Fn siginterrupt
	50	function
	51	is used to change the system call restart
	52	behavior when a system call is interrupted by the specified signal.
	53	If the flag is false (0), then system calls will be restarted if
	54	they are interrupted by the specified signal
	55	and no data has been transferred yet.
	56	System call restart has been the default behavior since
	57	.Bx 4.2 ,
	58	and is the default behaviour for
	59	.Xr signal 3
	60	on
	61	.Fx .
	62	.Pp
	63	If the flag is true (1),
	64	then restarting of system calls is disabled.
65	If a system call is interrupted by the specified signal
66	and no data has been transferred,
67	the system call will return \-1 with the global variable
68	.Va errno
69	set to
70	.Er EINTR .
71	Interrupted system calls that have started transferring
72	data will return the amount of data actually transferred.
73	System call interrupt is the signal behavior found on
74	.Bx 4.1
75	and
76	.At V
77	systems.
78	.Pp
79	Note that the new
80	.Bx 4.2
81	signal handling semantics are not
82	altered in any other way.
83	Most notably, signal handlers always remain installed until
84	explicitly changed by a subsequent
85	.Xr sigaction 2
86	call, and the signal mask operates as documented in
87	.Xr sigaction 2 .
88	Programs may switch between restartable and interruptible
89	system call operation as often as desired in the execution of a program.
90	.Pp
91	Issuing a
92	.Fn siginterrupt 3
93	call during the execution of a signal handler will cause
94	the new action to take place on the next signal to be caught.
95	.Sh NOTES
96	This library routine uses an extension of the
97	.Xr sigaction 2
98	system call that is not available in
99	.Bx 4.2 ;
100	hence, it should not be used if backward compatibility is needed.
101	.Sh RETURN VALUES
102	.Rv -std siginterrupt
103	.Sh ERRORS
104	The
105	.Fn siginterrupt
106	call fails if:
107	.Bl -tag -width Er
108	.It Bq Er EINVAL
109	The
110	.Fa sig
111	argument
112	is not a valid signal number.
113	.El
114	.Sh SEE ALSO
115	.Xr sigaction 2 ,
116	.Xr sigblock 2 ,
117	.Xr sigpause 2 ,
118	.Xr sigsetmask 2 ,
119	.Xr signal 3
120	.Sh HISTORY
121	The
122	.Fn siginterrupt
123	function appeared in
124	.Bx 4.3 .