1994-05-27 05:00:24 +00:00
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.\" Copyright (c) 1985, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)siginterrupt.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 4, 1993
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.Dt SIGINTERRUPT 3
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.Os BSD 4.3
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.Sh NAME
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.Nm siginterrupt
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.Nd allow signals to interrupt system calls
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.Sh SYNOPSIS
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.Fd #include <signal.h>
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.Ft int
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.Fn siginterrupt "int sig" "int flag"
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.Sh DESCRIPTION
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The
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.Fn siginterrupt
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function
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is used to change the system call restart
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behavior when a system call is interrupted by the specified signal.
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If the flag is false (0), then system calls will be restarted if
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they are interrupted by the specified signal
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and no data has been transferred yet.
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1996-12-15 23:23:17 +00:00
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System call restart has been the default behavior since
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.Bx 4.2 ,
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1997-08-13 18:40:57 +00:00
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and is the default behaviour for
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.Xr signal 3
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on
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1996-12-15 23:23:17 +00:00
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.Tn FreeBSD .
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1994-05-27 05:00:24 +00:00
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.Pp
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If the flag is true (1),
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then restarting of system calls is disabled.
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If a system call is interrupted by the specified signal
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and no data has been transferred,
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the system call will return \-1 with the global variable
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.Va errno
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set to
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.Dv EINTR .
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Interrupted system calls that have started transferring
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data will return the amount of data actually transferred.
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System call interrupt is the signal behavior found on
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.Bx 4.1
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and
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.At V
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systems.
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.Pp
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Note that the new
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.Bx 4.2
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signal handling semantics are not
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altered in any other way.
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Most notably, signal handlers always remain installed until
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explicitly changed by a subsequent
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.Xr sigaction 2
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call, and the signal mask operates as documented in
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.Xr sigaction 2 .
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Programs may switch between restartable and interruptible
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system call operation as often as desired in the execution of a program.
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.Pp
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Issuing a
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.Fn siginterrupt 3
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call during the execution of a signal handler will cause
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the new action to take place on the next signal to be caught.
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.Sh NOTES
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This library routine uses an extension of the
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.Xr sigaction 2
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system call that is not available in
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.Bx 4.2 ,
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hence it should not be used if backward compatibility is needed.
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.Sh RETURN VALUES
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A 0 value indicates that the call succeeded.
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A \-1 value indicates that an invalid signal number has been supplied.
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.Sh SEE ALSO
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.Xr sigaction 2 ,
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.Xr sigblock 2 ,
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1997-08-13 18:40:57 +00:00
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.Xr signal 3 ,
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1994-05-27 05:00:24 +00:00
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.Xr sigpause 2 ,
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.Xr sigsetmask 2 .
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.Sh HISTORY
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The
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.Fn siginterrupt
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function appeared in
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.Bx 4.3 .
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