initial import of NetBSD tree

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+.\"	$NetBSD: close.2,v 1.5 1995/02/27 12:32:14 cgd Exp $
+.\"
+.\" Copyright (c) 1980, 1991, 1993, 1994
+.\"	The Regents of the University of California.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed by the University of
+.\"	California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"     @(#)close.2	8.2 (Berkeley) 4/19/94
+.\"
+.Dd April 19, 1994
+.Dt CLOSE 2
+.Os BSD 4
+.Sh NAME
+.Nm close
+.Nd delete a descriptor
+.Sh SYNOPSIS
+.Fd #include <unistd.h>
+.Ft int
+.Fn close "int d"
+.Sh DESCRIPTION
+The
+.Fn close
+call deletes a descriptor from the per-process object
+reference table.
+If this is the last reference to the underlying object, the
+object will be deactivated.
+For example, on the last close of a file
+the current
+.Em seek
+pointer associated with the file is lost;
+on the last close of a
+.Xr socket 2
+associated naming information and queued data are discarded;
+on the last close of a file holding an advisory lock
+the lock is released (see further
+.Xr flock 2 ) .
+.Pp
+When a process exits,
+all associated file descriptors are freed, but since there is
+a limit on active descriptors per processes, the
+.Fn close
+function call
+is useful when a large quantity of file descriptors are being handled.
+.Pp
+When a process forks (see
+.Xr fork 2 ) ,
+all descriptors for the new child process reference the same
+objects as they did in the parent before the fork.
+If a new process is then to be run using
+.Xr execve 2 ,
+the process would normally inherit these descriptors.  Most
+of the descriptors can be rearranged with
+.Xr dup2 2
+or deleted with
+.Fn close
+before the
+.Xr execve
+is attempted, but if some of these descriptors will still
+be needed if the execve fails, it is necessary to arrange for them
+to be closed if the execve succeeds.
+For this reason, the call
+.Dq Li fcntl(d, F_SETFD, 1)
+is provided,
+which arranges that a descriptor will be closed after a successful
+execve; the call
+.Dq Li fcntl(d, F_SETFD, 0)
+restores the default,
+which is to not close the descriptor.
+.Sh RETURN VALUES
+Upon successful completion, a value of 0 is returned.
+Otherwise, a value of -1 is returned and the global integer variable
+.Va errno
+is set to indicate the error.
+.Sh ERRORS
+.Fn Close
+will fail if:
+.Bl -tag -width Er
+.It Bq Er EBADF
+.Fa D
+is not an active descriptor.
+.It Bq Er EINTR
+An interrupt was received.
+.El
+.Sh SEE ALSO
+.Xr accept 2 ,
+.Xr flock 2 ,
+.Xr open 2 ,
+.Xr pipe 2 ,
+.Xr socket 2 ,
+.Xr socketpair 2 ,
+.Xr execve 2 ,
+.Xr fcntl 2
+.Sh STANDARDS
+.Fn Close
+conforms to 
+.St -p1003.1-88 .