freebsd-dev/lib/libc/sys/close.2

.\" 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
.\" $FreeBSD$
.\"
.Dd December 1, 2017
.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 fd"
.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 fd
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 v1 .
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" 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.`
Renumber copyright clause 4 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 2017-02-28 23:42:47 +00:00			`.\" 3. Neither the name of the University nor the names of its contributors`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" 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`
$Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00			`.\" $FreeBSD$`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\"`
Mark all the system calls that were in 1st Edition Unix as such in the HISTORY section. Note: Any system calls that were added prior to v7, but after v1 weren't changed. Obtained from: http://www.tuhs.org/cgi-bin/utree.pl?file=V1/man/man2 2017-12-01 22:26:36 +00:00			`.Dd December 1, 2017`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Dt CLOSE 2`
mdoc(7) police: removed HISTORY info from the .Os call. 2001-07-10 13:41:46 +00:00			`.Os`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh NAME`
			`.Nm close`
			`.Nd delete a descriptor`
Introduce ".Lb" macro to libc manpages. More libraries manpages updates following. 2000-04-21 09:42:15 +00:00			`.Sh LIBRARY`
			`.Lb libc`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh SYNOPSIS`
mdoc(7) police: Use the new .In macro for #include statements. 2001-10-01 16:09:29 +00:00			`.In unistd.h`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Ft int`
Consistently reference file descriptors as "fd". 55 other manpages used "fd", while these used "d" and "filedes". MFC after: 1 week Approved by: gjb Approved by: re (delphij) 2013-09-12 00:53:38 +00:00			`.Fn close "int fd"`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh DESCRIPTION`
			`The`
			`.Fn close`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call deletes a descriptor from the per-process object`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`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 ) .`
Note the effect of close(2) on fcntl(2) record locks. PR: docs/3522 1999-05-04 17:45:12 +00:00			`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.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.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`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`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 ,`
Mechanically kill hard sentence breaks. 2004-07-02 23:52:20 +00:00			`the process would normally inherit these descriptors.`
			`Most`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`of the descriptors can be rearranged with`
			`.Xr dup2 2`
			`or deleted with`
			`.Fn close`
			`before the`
Added missing section numbers to a bunch of .Xr macros, or converted them into .Fn macros where appropriate. Also fixed up some minor formatting problems. 1996-03-27 20:49:07 +00:00			`.Xr execve 2`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`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`
Correct a call to fcntl(F_SETFD) to use `FD_CLOEXEC' instead of `1'. 2002-07-03 08:15:55 +00:00			`.Dq Li fcntl(d, F_SETFD, FD_CLOEXEC)`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`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`
Use the ``.Rv -std'' mdoc(7) macro in appropriate cases. Reviewed by: ru 2001-08-09 13:32:13 +00:00			`.Rv -std close`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh ERRORS`
The .Fn function. 2002-07-15 20:59:12 +00:00			`The`
			`.Fn close`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call will fail if:`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Bl -tag -width Er`
			`.It Bq Er EBADF`
mdoc(7) police: "The .Fa argument.". 2002-12-19 09:40:28 +00:00			`The`
Consistently reference file descriptors as "fd". 55 other manpages used "fd", while these used "d" and "filedes". MFC after: 1 week Approved by: gjb Approved by: re (delphij) 2013-09-12 00:53:38 +00:00			`.Fa fd`
mdoc(7) police: "The .Fa argument.". 2002-12-19 09:40:28 +00:00			`argument`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`is not an active descriptor.`
			`.It Bq Er EINTR`
			`An interrupt was received.`
Document ENOSPC. PR: 52612 Submitted by: Marc Olzheim <marcolz@ilse.nl> 2003-06-13 22:41:12 +00:00			`.It Bq Er ENOSPC`
			`The underlying object did not fit, cached data was lost.`
document recent change to return ECONNRESET for tcp sockets MFC after: 1 month 2006-12-04 18:39:11 +00:00			`.It Bq Er ECONNRESET`
Grammar. OK'ed by: sam 2006-12-04 20:34:25 +00:00			`The underlying object was a stream socket that was shut down by the peer`
document recent change to return ECONNRESET for tcp sockets MFC after: 1 month 2006-12-04 18:39:11 +00:00			`before all pending data was delivered.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.El`
Clarify the implementation-defined behaviour in case of close(2) returning error. MFC after: 1 week 2012-01-22 11:58:17 +00:00			`.Pp`
			`In case of any error except`
			`.Er EBADF ,`
			`the supplied file descriptor is deallocated and therefore is no longer valid.`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh SEE ALSO`
			`.Xr accept 2 ,`
Add a new 'void closefrom(int lowfd)' system call. When called, it closes any open file descriptors >= 'lowfd'. It is largely identical to the same function on other operating systems such as Solaris, DFly, NetBSD, and OpenBSD. One difference from other *BSD is that this closefrom() does not fail with any errors. In practice, while the manpages for NetBSD and OpenBSD claim that they return EINTR, they ignore internal errors from close() and never return EINTR. DFly does return EINTR, but for the common use case (closing fd's prior to execve()), the caller really wants all fd's closed and returning EINTR just forces callers to call closefrom() in a loop until it stops failing. Note that this implementation of closefrom(2) does not make any effort to resolve userland races with open(2) in other threads. As such, it is not multithread safe. Submitted by: rwatson (initial version) Reviewed by: rwatson MFC after: 2 weeks 2009-06-15 20:38:55 +00:00			`.Xr closefrom 2 ,`
Sort cross references. 1997-01-20 23:23:22 +00:00			`.Xr execve 2 ,`
			`.Xr fcntl 2 ,`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Xr flock 2 ,`
			`.Xr open 2 ,`
			`.Xr pipe 2 ,`
			`.Xr socket 2 ,`
Sort cross references. 1997-01-20 23:23:22 +00:00			`.Xr socketpair 2`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh STANDARDS`
upgrade STANDARDS from POSIX 1003.1-88 to 1003.1-90 using .St macro use ``is expected to conform to'' phrase, not ``conforms to'' Pointed out by: Bruce->NIST-PCTS 1996-12-02 20:03:58 +00:00			`The`
			`.Fn close`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call is expected to conform to`
upgrade STANDARDS from POSIX 1003.1-88 to 1003.1-90 using .St macro use ``is expected to conform to'' phrase, not ``conforms to'' Pointed out by: Bruce->NIST-PCTS 1996-12-02 20:03:58 +00:00			`.St -p1003.1-90 .`
function appeared in Version 7 AT&T UNIX Obtained from: ftp://netlib.att.com/netlib/att/cs/v7man/man2 1996-08-29 21:24:19 +00:00			`.Sh HISTORY`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`The`
function appeared in Version 7 AT&T UNIX Obtained from: ftp://netlib.att.com/netlib/att/cs/v7man/man2 1996-08-29 21:24:19 +00:00			`.Fn close`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`function appeared in`
Mark all the system calls that were in 1st Edition Unix as such in the HISTORY section. Note: Any system calls that were added prior to v7, but after v1 weren't changed. Obtained from: http://www.tuhs.org/cgi-bin/utree.pl?file=V1/man/man2 2017-12-01 22:26:36 +00:00			`.At v1 .`