145 lines
4.3 KiB
Groff
145 lines
4.3 KiB
Groff
.\" 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.
|
|
.\" 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
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd January 22, 2012
|
|
.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 further
|
|
.Xr flock 2 ) .
|
|
However, the semantics of System V and
|
|
.St -p1003.1-88
|
|
dictate that all
|
|
.Xr fcntl 2
|
|
advisory record locks associated with a file for a given process
|
|
are removed when
|
|
.Em any
|
|
file descriptor for that file is closed by that process.
|
|
.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
|
|
system 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 2
|
|
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, FD_CLOEXEC)
|
|
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
|
|
.Rv -std close
|
|
.Sh ERRORS
|
|
The
|
|
.Fn close
|
|
system call will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
The
|
|
.Fa d
|
|
argument
|
|
is not an active descriptor.
|
|
.It Bq Er EINTR
|
|
An interrupt was received.
|
|
.It Bq Er ENOSPC
|
|
The underlying object did not fit, cached data was lost.
|
|
.It Bq Er ECONNRESET
|
|
The underlying object was a stream socket that was shut down by the peer
|
|
before all pending data was delivered.
|
|
.El
|
|
.Pp
|
|
In case of any error except
|
|
.Er EBADF ,
|
|
the supplied file descriptor is deallocated and therefore is no longer valid.
|
|
.Sh SEE ALSO
|
|
.Xr accept 2 ,
|
|
.Xr closefrom 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
|
|
system call is expected to conform to
|
|
.St -p1003.1-90 .
|
|
.Sh HISTORY
|
|
The
|
|
.Fn close
|
|
function appeared in
|
|
.At v7 .
|