bsd_signal.3: ATTRIBUTES: Note function that is thread-safe

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

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.TH BSD_SIGNAL 3 2013-10-22 "" "Linux Programmer's Manual"
.SH NAME
bsd_signal \- signal handling with BSD semantics
.SH SYNOPSIS
.BR "#define _XOPEN_SOURCE" "       /* See feature_test_macros(7) */"
.br
.B #include <signal.h>
.sp
.B typedef void (*sighandler_t)(int);
.sp
.BI "sighandler_t bsd_signal(int " signum ", sighandler_t " handler );
.SH DESCRIPTION
The
.BR bsd_signal ()
function takes the same arguments, and performs the same task, as
.BR signal (2).

The difference between the two is that
.BR bsd_signal ()
is guaranteed to provide reliable signal semantics, that is:
a) the disposition of the signal is not reset to the default
when the handler is invoked;
b) delivery of further instances of the signal is blocked while
the signal handler is executing; and
c) if the handler interrupts a blocking system call,
then the system call is automatically restarted.
A portable application cannot rely on
.BR signal (2)
to provide these guarantees.
.SH RETURN VALUE
The
.BR bsd_signal ()
function returns the previous value of the signal handler, or
.B SIG_ERR
on error.
.SH ERRORS
As for
.BR signal (2).
.SH ATTRIBUTES
.SS Multithreading (see pthreads(7))
The
.BR bsd_signal ()
function is thread-safe.
.SH CONFORMING TO
4.2BSD, POSIX.1-2001.
POSIX.1-2008 removes the specification of
.BR bsd_signal (),
recommending the use of
.BR sigaction (2)
instead.
.SH NOTES
Use of
.BR bsd_signal ()
should be avoided; use
.BR sigaction (2)
instead.

On modern Linux systems,
.BR bsd_signal ()
and
.BR signal (2)
are equivalent.
But on older systems,
.BR signal (2)
provided unreliable signal semantics; see
.BR signal (2)
for details.

The use of
.I sighandler_t
is a GNU extension;
this type is defined only if the
.B _GNU_SOURCE
feature test macro is defined.
.SH SEE ALSO
.BR sigaction (2),
.BR signal (2),
.BR sysv_signal (3),
.BR signal (7)