133 lines
3.9 KiB
Groff
133 lines
3.9 KiB
Groff
.\" $NetBSD: close.2,v 1.17 2004/06/01 16:14:10 kleink 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. 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
|
|
.Sh NAME
|
|
.Nm close
|
|
.Nd delete a descriptor
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In unistd.h
|
|
.Ft int
|
|
.Fn close "int d"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn close
|
|
system 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
|
|
.Xr flock 2 ) .
|
|
.Pp
|
|
When a process exits, all associated descriptors are freed, but
|
|
since there is a limit on active descriptors per processes, the
|
|
.Fn close
|
|
system call
|
|
is useful when a large quantity of file descriptors are being handled.
|
|
.Pp
|
|
When a process calls
|
|
.Xr fork 2 ,
|
|
all descriptors for the new child process reference the same
|
|
objects as they did in the parent before the
|
|
.Fn 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
|
|
.Fn execve
|
|
is attempted, but if some of these descriptors will still be needed if the
|
|
.Fn execve
|
|
fails, it is necessary to arrange for them to be closed only if the
|
|
.Fn execve
|
|
succeeds.
|
|
For this reason, the system call
|
|
.Bl -item -offset indent
|
|
.It
|
|
.Fn fcntl d F_SETFD 1 ;
|
|
.El
|
|
.Pp
|
|
is provided,
|
|
which arranges that a descriptor
|
|
.Dq Fa d
|
|
will be closed after a successful
|
|
.Fn execve ;
|
|
the system call
|
|
.Bl -item -offset indent
|
|
.It
|
|
.Fn fcntl d F_SETFD 0 ;
|
|
.El
|
|
.Pp
|
|
restores the default, which is to not close descriptor
|
|
.Dq Fa d .
|
|
.Sh RETURN VALUES
|
|
Upon successful completion, a value of 0 is returned.
|
|
Otherwise, a value of \-1 is returned and
|
|
.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 execve 2 ,
|
|
.Xr fcntl 2 ,
|
|
.Xr flock 2 ,
|
|
.Xr open 2 ,
|
|
.Xr pipe 2 ,
|
|
.Xr socket 2 ,
|
|
.Xr socketpair 2
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn close
|
|
function conforms to
|
|
.St -p1003.1-90 .
|