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Documentation of bsd_signal().
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.\" Copyright (c) 2007 Michael Kerrisk <mtk-manpages@gmx.net>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH BSD_SIGNAL 2 2007-05-04 "" "Linux Programmer's Manual"
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.SH NAME
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bsd_signal \- signal handling with BSD semantics
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.SH SYNOPSIS
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.B #define _XOPEN_SOURCE
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.br
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.B #include <signal.h>
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.sp
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.B typedef void (*sighandler_t)(int);
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.sp
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.BI "sighandler_t bsd_signal(int " signum ", sighandler_t " handler );
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.SH DESCRIPTION
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The
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.BR bsd_signal ()
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function takes the same arguments, and performs the same task, as
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.BR signal (2).
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The difference between the two is that
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.BR bsd_signal ()
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is guaranteed to provide reliable signal semantics, that is:
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a) the disposition of the signal is not reset to the default
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when the handler is invoked;
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b) delivery of further instances of the signal is blocked while
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the signal handler is executing; and
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c) if the handler interrupts a blocking system call,
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then the system call is automatically restarted.
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A portable application cannot rely on
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.BR signal (2)
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to provide these guarantees.
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.SH "RETURN VALUE"
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The
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.BR bsd_signal ()
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function returns the previous value of the signal handler, or
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.B SIG_ERR
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on error.
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.SH ERRORS
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As for
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.BR signal (2).
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.SH NOTES
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Use of
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.BR bsd_signal ()
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should be avoided; use
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.BR sigaction (2)
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instead.
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On modern Linux systems,
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.BR bsd_signal ()
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and
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.BR signal (2)
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are equivalent.
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But on older systems,
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.BR signal (2)
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provided unreliable signal semantics; see
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.BR signal (2)
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for details.
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The use of
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.B sighandler_t
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is a GNU extension;
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this type is only defined if
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the _GNU_SOURCE feature test macro is defined.
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.SH "CONFORMING TO"
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4.2BSD, POSIX.1-2001.
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.SH "SEE ALSO"
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.BR sigaction (2),
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.BR signal (2),
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.BR sysv_signal (3),
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.BR feature_test_macros (7),
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.BR signal (7)
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.\" FIXME add SEE ALSO refs from those pages.
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