[thirdparty/man-pages.git] / man3 / sysv_signal.3

.\" Copyright (c) 2007 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.TH SYSV_SIGNAL 3 2007-05-04 "" "Linux Programmer's Manual"
.SH NAME
sysv_signal \- signal handling with System V semantics
.SH SYNOPSIS
.B #define _GNU_SOURCE
.br
.B #include <signal.h>
.sp
.B typedef void (*sighandler_t)(int);
.sp
.BI "sighandler_t sysv_signal(int " signum ", sighandler_t " handler );
.SH DESCRIPTION
The
.BR sysv_signal ()
function takes the same arguments, and performs the same task, as
.BR signal (2).

However
.BR sysv_signal ()
provides the System V unreliable signal semantics, that is:
a) the disposition of the signal is reset to the default
when the handler is invoked;
b) delivery of further instances of the signal is not blocked while
the signal handler is executing; and
c) if the handler interrupts (certain) blocking system calls,
then the system call is not automatically restarted.
.SH "RETURN VALUE"
The
.BR sysv_signal ()
function returns the previous value of the signal handler, or
.B SIG_ERR
on error.
.SH ERRORS
As for
.BR signal (2).
.SH "CONFORMING TO"
This function is non-standard.
.SH NOTES
Use of
.BR sysv_signal ()
should be avoided; use
.BR sigaction (2)
instead.

On older Linux systems,
.BR sysv_signal ()
and
.BR signal (2)
were equivalent.
But on newer systems,
.BR signal (2)
provides reliable signal semantics; see
.BR signal (2)
for details.

The use of
.I sighandler_t
is a GNU extension;
this type is only defined if
the
.B _GNU_SOURCE
feature test macro is defined.
.SH "SEE ALSO"
.BR sigaction (2),
.BR signal (2),
.BR bsd_signal (3),
.BR feature_test_macros (7),
.BR signal (7)
Commit	Line	Data
c11b1abf	1	.\" Copyright (c) 2007 Michael Kerrisk <mtk.manpages@gmail.com>
7594eb92 MK	2	.\"
	3	.\" Permission is granted to make and distribute verbatim copies of this
	4	.\" manual provided the copyright notice and this permission notice are
	5	.\" preserved on all copies.
	6	.\"
	7	.\" Permission is granted to copy and distribute modified versions of this
	8	.\" manual under the conditions for verbatim copying, provided that the
	9	.\" entire resulting derived work is distributed under the terms of a
	10	.\" permission notice identical to this one.
	11	.\"
	12	.\" Since the Linux kernel and libraries are constantly changing, this
	13	.\" manual page may be incorrect or out-of-date. The author(s) assume no
	14	.\" responsibility for errors or omissions, or for damages resulting from
	15	.\" the use of the information contained herein. The author(s) may not
	16	.\" have taken the same level of care in the production of this manual,
	17	.\" which is licensed free of charge, as they might when working
	18	.\" professionally.
	19	.\"
	20	.\" Formatted or processed versions of this manual, if unaccompanied by
	21	.\" the source, must acknowledge the copyright and authors of this work.
	22	.\"
b8b64c11	23	.TH SYSV_SIGNAL 3 2007-05-04 "" "Linux Programmer's Manual"
7594eb92 MK	24	.SH NAME
	25	sysv_signal \- signal handling with System V semantics
	26	.SH SYNOPSIS
	27	.B #define _GNU_SOURCE
	28	.br
	29	.B #include <signal.h>
	30	.sp
	31	.B typedef void (*sighandler_t)(int);
	32	.sp
	33	.BI "sighandler_t sysv_signal(int " signum ", sighandler_t " handler );
	34	.SH DESCRIPTION
	35	The
	36	.BR sysv_signal ()
	37	function takes the same arguments, and performs the same task, as
	38	.BR signal (2).
	39
	40	However
	41	.BR sysv_signal ()
	42	provides the System V unreliable signal semantics, that is:
	43	a) the disposition of the signal is reset to the default
	44	when the handler is invoked;
	45	b) delivery of further instances of the signal is not blocked while
	46	the signal handler is executing; and
	47	c) if the handler interrupts (certain) blocking system calls,
	48	then the system call is not automatically restarted.
	49	.SH "RETURN VALUE"
	50	The
	51	.BR sysv_signal ()
	52	function returns the previous value of the signal handler, or
	53	.B SIG_ERR
	54	on error.
	55	.SH ERRORS
	56	As for
	57	.BR signal (2).
2b2581ee MK	58	.SH "CONFORMING TO"
2b2581ee MK	59	This function is non-standard.
7594eb92 MK	60	.SH NOTES
	61	Use of
	62	.BR sysv_signal ()
	63	should be avoided; use
	64	.BR sigaction (2)
	65	instead.
	66
	67	On older Linux systems,
	68	.BR sysv_signal ()
	69	and
	70	.BR signal (2)
	71	were equivalent.
988db661	72	But on newer systems,
7594eb92 MK	73	.BR signal (2)
	74	provides reliable signal semantics; see
	75	.BR signal (2)
	76	for details.
	77
	78	The use of
f19a0f03	79	.I sighandler_t
7594eb92	80	is a GNU extension;
988db661	81	this type is only defined if
c3dfd2c8 MK	82	the
	83	.B _GNU_SOURCE
	84	feature test macro is defined.
7594eb92 MK	85	.SH "SEE ALSO"
	86	.BR sigaction (2),
	87	.BR signal (2),
	88	.BR bsd_signal (3),
	89	.BR feature_test_macros (7),
	90	.BR signal (7)