mirror of
https://github.com/freebsd/freebsd-src.git
synced 2024-12-02 04:13:39 +00:00
172 lines
4.6 KiB
Groff
172 lines
4.6 KiB
Groff
.\"
|
|
.\" 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.
|
|
.\"
|
|
.\" @(#)mount_fdesc.8 8.2 (Berkeley) 3/27/94
|
|
.\"
|
|
.\"
|
|
.Dd March 27, 1994
|
|
.Dt MOUNT_FDESC 8
|
|
.Os BSD 4.4
|
|
.Sh NAME
|
|
.Nm mount_fdesc
|
|
.Nd mount the file-descriptor file system
|
|
.Sh SYNOPSIS
|
|
.Nm mount_fdesc
|
|
.Op Fl o Ar options
|
|
.Ar fdesc
|
|
.Ar mount_point
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm mount_fdesc
|
|
command attaches an instance of the per-process file descriptor
|
|
namespace to the global filesystem namespace.
|
|
The conventional mount point is
|
|
.Pa /dev
|
|
and the filesystem should be union mounted in order to augment,
|
|
rather than replace, the existing entries in
|
|
.Pa /dev .
|
|
This command is normally executed by
|
|
.Xr mount 8
|
|
at boot time.
|
|
.Pp
|
|
The options are as follows:
|
|
.Bl -tag -width indent
|
|
.It Fl o
|
|
Options are specified with a
|
|
.Fl o
|
|
flag followed by a comma separated string of options.
|
|
See the
|
|
.Xr mount 8
|
|
man page for possible options and their meanings.
|
|
.El
|
|
.Pp
|
|
The contents of the mount point are
|
|
.Pa fd ,
|
|
.Pa stderr ,
|
|
.Pa stdin ,
|
|
.Pa stdout
|
|
and
|
|
.Pa tty .
|
|
.Pp
|
|
.Pa fd
|
|
is a directory whose 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
|
|
The files
|
|
.Pa /dev/stdin ,
|
|
.Pa /dev/stdout
|
|
and
|
|
.Pa /dev/stderr
|
|
appear as symlinks to the relevant entry in the
|
|
.Pa /dev/fd
|
|
sub-directory.
|
|
Opening them is equivalent to the following calls:
|
|
.Bd -literal -offset indent
|
|
fd = fcntl(STDIN_FILENO, F_DUPFD, 0);
|
|
fd = fcntl(STDOUT_FILENO, F_DUPFD, 0);
|
|
fd = fcntl(STDERR_FILENO, F_DUPFD, 0);
|
|
.Ed
|
|
.Pp
|
|
Flags to the
|
|
.Xr open 2
|
|
call other than
|
|
.Dv O_RDONLY ,
|
|
.Dv O_WRONLY
|
|
and
|
|
.Dv O_RDWR
|
|
are ignored.
|
|
.Pp
|
|
The
|
|
.Pa /dev/tty
|
|
entry is an indirect reference to the current process's controlling terminal.
|
|
It appears as a named pipe (FIFO) but behaves in exactly the same way as
|
|
the real controlling terminal device.
|
|
.Sh FILES
|
|
.Bl -tag -width /dev/stderr -compact
|
|
.It Pa /dev/fd/#
|
|
.It Pa /dev/stdin
|
|
.It Pa /dev/stdout
|
|
.It Pa /dev/stderr
|
|
.It Pa /dev/tty
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr mount 2 ,
|
|
.Xr unmount 2 ,
|
|
.Xr tty 4 ,
|
|
.Xr fstab 5 ,
|
|
.Xr mount 8
|
|
.Sh CAVEATS
|
|
No
|
|
.Pa .
|
|
and
|
|
.Pa ..
|
|
entries appear when listing the contents of the
|
|
.Pa /dev/fd
|
|
directory.
|
|
This makes sense in the context of this filesystem, but is inconsistent
|
|
with usual filesystem conventions.
|
|
However, it is still possible to refer to both
|
|
.Pa .
|
|
and
|
|
.Pa ..
|
|
in a pathname.
|
|
.Pp
|
|
This filesystem may not be NFS-exported.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm mount_fdesc
|
|
utility first appeared in 4.4BSD.
|