7e6cabd06e
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
145 lines
4.3 KiB
Groff
145 lines
4.3 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993, 1994
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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. 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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.\" @(#)close.2 8.2 (Berkeley) 4/19/94
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.\" $FreeBSD$
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.\"
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.Dd September 11, 2013
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.Dt CLOSE 2
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.Os
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.Sh NAME
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.Nm close
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.Nd delete a descriptor
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn close "int fd"
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.Sh DESCRIPTION
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The
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.Fn close
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system call deletes a descriptor from the per-process object
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reference table.
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If this is the last reference to the underlying object, the
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object will be deactivated.
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For example, on the last close of a file
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the current
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.Em seek
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pointer associated with the file is lost;
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on the last close of a
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.Xr socket 2
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associated naming information and queued data are discarded;
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on the last close of a file holding an advisory lock
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the lock is released (see further
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.Xr flock 2 ) .
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However, the semantics of System V and
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.St -p1003.1-88
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dictate that all
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.Xr fcntl 2
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advisory record locks associated with a file for a given process
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are removed when
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.Em any
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file descriptor for that file is closed by that process.
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.Pp
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When a process exits,
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all associated file descriptors are freed, but since there is
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a limit on active descriptors per processes, the
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.Fn close
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system call
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is useful when a large quantity of file descriptors are being handled.
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.Pp
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When a process forks (see
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.Xr fork 2 ) ,
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all descriptors for the new child process reference the same
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objects as they did in the parent before the fork.
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If a new process is then to be run using
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.Xr execve 2 ,
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the process would normally inherit these descriptors.
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Most
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of the descriptors can be rearranged with
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.Xr dup2 2
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or deleted with
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.Fn close
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before the
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.Xr execve 2
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is attempted, but if some of these descriptors will still
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be needed if the execve fails, it is necessary to arrange for them
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to be closed if the execve succeeds.
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For this reason, the call
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.Dq Li fcntl(d, F_SETFD, FD_CLOEXEC)
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is provided,
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which arranges that a descriptor will be closed after a successful
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execve; the call
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.Dq Li fcntl(d, F_SETFD, 0)
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restores the default,
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which is to not close the descriptor.
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.Sh RETURN VALUES
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.Rv -std close
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.Sh ERRORS
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The
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.Fn close
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system call will fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa fd
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argument
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is not an active descriptor.
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.It Bq Er EINTR
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An interrupt was received.
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.It Bq Er ENOSPC
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The underlying object did not fit, cached data was lost.
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.It Bq Er ECONNRESET
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The underlying object was a stream socket that was shut down by the peer
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before all pending data was delivered.
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.El
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.Pp
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In case of any error except
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.Er EBADF ,
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the supplied file descriptor is deallocated and therefore is no longer valid.
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.Sh SEE ALSO
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.Xr accept 2 ,
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.Xr closefrom 2 ,
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.Xr execve 2 ,
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.Xr fcntl 2 ,
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.Xr flock 2 ,
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.Xr open 2 ,
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.Xr pipe 2 ,
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.Xr socket 2 ,
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.Xr socketpair 2
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.Sh STANDARDS
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The
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.Fn close
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system call is expected to conform to
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.St -p1003.1-90 .
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.Sh HISTORY
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The
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.Fn close
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function appeared in
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.At v7 .
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