freebsd-skq/share/man/man5/fdescfs.5

.\" Copyright (c) 1996
.\"	Mike Pritchard <mpp@FreeBSD.org>.  All rights reserved.
.\"
.\" Copyright (c) 1992, 1993, 1994
.\"	The Regents of the University of California.  All rights reserved.
.\" All rights reserved.
.\"
.\" This code is derived from software donated to Berkeley by
.\" Jan-Simon Pendry.
.\"
.\" 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.
.\"
.\" $FreeBSD$
.\"
.Dd September 18, 2010
.Dt FDESCFS 5
.Os
.Sh NAME
.Nm fdescfs
.Nd file-descriptor file system
.Sh SYNOPSIS
.Bd -literal
fdescfs	/dev/fd	fdescfs rw 0 0
.Ed
.Sh DESCRIPTION
The file-descriptor file system, or
.Nm ,
provides access to the per-process file descriptor
namespace in the global file system namespace.
The conventional mount point is
.Pa /dev/fd .
.Pp
The file system's contents
appear as a list of numbered files
which correspond to the open files of the process reading the
directory.
The files
.Pa /dev/fd/0
through
.Pa /dev/fd/#
refer to file descriptors which can be accessed through the file
system.
If the file descriptor is open and the mode the file is being opened
with is a subset of the mode of the existing descriptor, the call:
.Bd -literal -offset indent
fd = open("/dev/fd/0", mode);
.Ed
.Pp
and the call:
.Bd -literal -offset indent
fd = fcntl(0, F_DUPFD, 0);
.Ed
.Pp
are equivalent.
.Pp
Flags to the
.Xr open 2
call other than
.Dv O_RDONLY ,
.Dv O_WRONLY
and
.Dv O_RDWR
are ignored.
.Pp
.Em "Note:"
.Pa /dev/fd/0 ,
.Pa /dev/fd/1
and
.Pa /dev/fd/2
files are created by default when devfs alone is mounted.
.Nm
creates entries for all file descriptors opened by the process.
.Sh FILES
.Bl -tag -width /dev/stderr -compact
.It Pa /dev/fd/#
.El
.Sh EXAMPLES
To mount a  
.Nm
volume located on
.Pa /dev/fd :
.Pp
.Dl "mount -t fdescfs null /dev/fd"
.Sh SEE ALSO
.Xr devfs 5 ,
.Xr mount 8
.Sh HISTORY
The
.Nm
file system first appeared in
.Bx 4.4 .
The
.Nm
manual page first appeared in
.Fx 2.2 .
.Sh AUTHORS
.An -nosplit
The
.Nm
manual page was written by
.An Mike Pritchard Aq mpp@FreeBSD.org ,
and was based on the
manual page written by
.An Jan-Simon Pendry .
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.\" Copyright (c) 1996`
			`.\" Mike Pritchard <mpp@FreeBSD.org>. All rights reserved.`
			`.\"`
			`.\" Copyright (c) 1992, 1993, 1994`
			`.\" The Regents of the University of California. All rights reserved.`
			`.\" All rights reserved.`
			`.\"`
			`.\" This code is derived from software donated to Berkeley by`
			`.\" Jan-Simon Pendry.`
			`.\"`
			`.\" 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.`
add missing cvs Id lines. 1997-03-07 03:28:23 +00:00			`.\"`
$Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00			`.\" $FreeBSD$`
add missing cvs Id lines. 1997-03-07 03:28:23 +00:00			`.\"`
Note that devfs(5) and fdescfs(5) both create /dev/fd file descriptors. PR: 144534 Submitted by: Matthew Seaman <m.seaman at infracaninophile co uk> Patch by: Matthew Seaman, keramida Approved by: keramida (mentor) MFC after: 1 week 2010-09-18 19:23:14 +00:00			`.Dd September 18, 2010`
Rename (after a repo-copy) some mount(8) programs: mount_fdesc -> mount_fdescfs mount_null -> mount_nullfs mount_portal -> mount_portalfs mount_umap -> mount_umapfs mount_union -> mount_unionfs 2001-05-23 14:58:19 +00:00			`.Dt FDESCFS 5`
			`.Os`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Sh NAME`
Rename (after a repo-copy) some mount(8) programs: mount_fdesc -> mount_fdescfs mount_null -> mount_nullfs mount_portal -> mount_portalfs mount_umap -> mount_umapfs mount_union -> mount_unionfs 2001-05-23 14:58:19 +00:00			`.Nm fdescfs`
Uniformly refer to a file system as "file system". Approved by: re 2002-12-12 17:26:04 +00:00			`.Nd file-descriptor file system`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Sh SYNOPSIS`
Deal with unsafe tab characters. 2004-07-02 19:55:26 +00:00			`.Bd -literal`
Rename (after a repo-copy) some mount(8) programs: mount_fdesc -> mount_fdescfs mount_null -> mount_nullfs mount_portal -> mount_portalfs mount_umap -> mount_umapfs mount_union -> mount_unionfs 2001-05-23 14:58:19 +00:00			`fdescfs /dev/fd fdescfs rw 0 0`
Deal with unsafe tab characters. 2004-07-02 19:55:26 +00:00			`.Ed`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Sh DESCRIPTION`
Uniformly refer to a file system as "file system". Approved by: re 2002-12-12 17:26:04 +00:00			`The file-descriptor file system, or`
mdoc(7) police: use the new features of the Nm macro. 2000-11-20 18:41:33 +00:00			`.Nm ,`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`provides access to the per-process file descriptor`
Uniformly refer to a file system as "file system". Approved by: re 2002-12-12 17:26:04 +00:00			`namespace in the global file system namespace.`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`The conventional mount point is`
Document the `new' fdesc--now that it belongs only on /dev/fd, remove all non-/dev/fd related documentation (such as that for stdin, stdout, tty). Update the fstab line to refer to /dev/fd instead of /dev. 2000-05-11 22:20:23 +00:00			`.Pa /dev/fd .`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Pp`
Uniformly refer to a file system as "file system". Approved by: re 2002-12-12 17:26:04 +00:00			`The file system's contents`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`appear as a list of numbered files`
			`which correspond to the open files of the process reading the`
			`directory.`
			`The files`
			`.Pa /dev/fd/0`
			`through`
			`.Pa /dev/fd/#`
			`refer to file descriptors which can be accessed through the file`
			`system.`
			`If the file descriptor is open and the mode the file is being opened`
			`with is a subset of the mode of the existing descriptor, the call:`
			`.Bd -literal -offset indent`
			`fd = open("/dev/fd/0", mode);`
			`.Ed`
			`.Pp`
			`and the call:`
			`.Bd -literal -offset indent`
			`fd = fcntl(0, F_DUPFD, 0);`
			`.Ed`
			`.Pp`
			`are equivalent.`
			`.Pp`
			`Flags to the`
			`.Xr open 2`
			`call other than`
Removed whitespace at end-of-line; no content changes. I simply did cd src/share; find man[1-9] -type f\|xargs perl -pi -e 's/[ \t]+$//' BTW, what editors are the culprits? I'm using vim and it shows me whitespace at EOL in troff files with a thick blue block... Reviewed by: Silence from cvs diff -b MFC after: 7 days 2001-07-14 19:41:16 +00:00			`.Dv O_RDONLY ,`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Dv O_WRONLY`
			`and`
			`.Dv O_RDWR`
			`are ignored.`
Note that devfs(5) and fdescfs(5) both create /dev/fd file descriptors. PR: 144534 Submitted by: Matthew Seaman <m.seaman at infracaninophile co uk> Patch by: Matthew Seaman, keramida Approved by: keramida (mentor) MFC after: 1 week 2010-09-18 19:23:14 +00:00			`.Pp`
			`.Em "Note:"`
			`.Pa /dev/fd/0 ,`
			`.Pa /dev/fd/1`
			`and`
			`.Pa /dev/fd/2`
			`files are created by default when devfs alone is mounted.`
			`.Nm`
			`creates entries for all file descriptors opened by the process.`
mdoc: move remaining sections into consistent order This pertains mostly to FILES, HISTORY, EXIT STATUS and AUTHORS sections. Found by: mdocml lint run Reviewed by: ru 2010-05-13 12:08:11 +00:00			`.Sh FILES`
			`.Bl -tag -width /dev/stderr -compact`
			`.It Pa /dev/fd/#`
			`.El`
Change reference from mount_devfs(8) to mount(8), and add an example. Remove reference to mount_fdescfs(8), since mount(8) calls nmount() directly to mount an fdescfs filesystem, instead of forking an external mount_fdescfs program. 2006-11-21 04:56:50 +00:00			`.Sh EXAMPLES`
			`To mount a`
			`.Nm`
			`volume located on`
			`.Pa /dev/fd :`
			`.Pp`
			`.Dl "mount -t fdescfs null /dev/fd"`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Sh SEE ALSO`
Note that devfs(5) and fdescfs(5) both create /dev/fd file descriptors. PR: 144534 Submitted by: Matthew Seaman <m.seaman at infracaninophile co uk> Patch by: Matthew Seaman, keramida Approved by: keramida (mentor) MFC after: 1 week 2010-09-18 19:23:14 +00:00			`.Xr devfs 5 ,`
Change reference from mount_devfs(8) to mount(8), and add an example. Remove reference to mount_fdescfs(8), since mount(8) calls nmount() directly to mount an fdescfs filesystem, instead of forking an external mount_fdescfs program. 2006-11-21 04:56:50 +00:00			`.Xr mount 8`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Sh HISTORY`
			`The`
Removed whitespace at end-of-line; no content changes. I simply did cd src/share; find man[1-9] -type f\|xargs perl -pi -e 's/[ \t]+$//' BTW, what editors are the culprits? I'm using vim and it shows me whitespace at EOL in troff files with a thick blue block... Reviewed by: Silence from cvs diff -b MFC after: 7 days 2001-07-14 19:41:16 +00:00			`.Nm`
Uniformly refer to a file system as "file system". Approved by: re 2002-12-12 17:26:04 +00:00			`file system first appeared in`
Various man page cleanup: - Sort xrefs - FreeBSD.ORG -> FreeBSD.org - Be consistent with section names as outlined in mdoc(7). - Other misc mdoc cleanup. PR: doc/13144 Submitted by: Alexey M. Zelkin <phantom@cris.net> 1999-08-15 10:48:36 +00:00			`.Bx 4.4 .`
Removed whitespace at end-of-line; no content changes. I simply did cd src/share; find man[1-9] -type f\|xargs perl -pi -e 's/[ \t]+$//' BTW, what editors are the culprits? I'm using vim and it shows me whitespace at EOL in troff files with a thick blue block... Reviewed by: Silence from cvs diff -b MFC after: 7 days 2001-07-14 19:41:16 +00:00			`The`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Nm`
Removed whitespace at end-of-line; no content changes. I simply did cd src/share; find man[1-9] -type f\|xargs perl -pi -e 's/[ \t]+$//' BTW, what editors are the culprits? I'm using vim and it shows me whitespace at EOL in troff files with a thick blue block... Reviewed by: Silence from cvs diff -b MFC after: 7 days 2001-07-14 19:41:16 +00:00			`manual page first appeared in`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Fx 2.2 .`
.Sh AUTHOR -> .Sh AUTHORS according to mdoc specs. Use .An/.Aq. 1998-03-12 07:31:21 +00:00			`.Sh AUTHORS`
mdoc(7) police: do not split author names in the AUTHORS section. 2000-11-22 09:35:58 +00:00			`.An -nosplit`
Removed whitespace at end-of-line; no content changes. I simply did cd src/share; find man[1-9] -type f\|xargs perl -pi -e 's/[ \t]+$//' BTW, what editors are the culprits? I'm using vim and it shows me whitespace at EOL in troff files with a thick blue block... Reviewed by: Silence from cvs diff -b MFC after: 7 days 2001-07-14 19:41:16 +00:00			`The`
Add fdesc(5) to document the file-descriptor file system. 1996-12-14 22:14:55 +00:00			`.Nm`
.Sh AUTHOR -> .Sh AUTHORS according to mdoc specs. Use .An/.Aq. 1998-03-12 07:31:21 +00:00			`manual page was written by`
			`.An Mike Pritchard Aq mpp@FreeBSD.org ,`
Removed whitespace at end-of-line; no content changes. I simply did cd src/share; find man[1-9] -type f\|xargs perl -pi -e 's/[ \t]+$//' BTW, what editors are the culprits? I'm using vim and it shows me whitespace at EOL in troff files with a thick blue block... Reviewed by: Silence from cvs diff -b MFC after: 7 days 2001-07-14 19:41:16 +00:00			`and was based on the`
.Sh AUTHOR -> .Sh AUTHORS according to mdoc specs. Use .An/.Aq. 1998-03-12 07:31:21 +00:00			`manual page written by`
			`.An Jan-Simon Pendry .`