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Diffstat (limited to 'sbin/mount_std/mount_fdesc.8')
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diff --git a/sbin/mount_std/mount_fdesc.8 b/sbin/mount_std/mount_fdesc.8 new file mode 100644 index 0000000..a61c952 --- /dev/null +++ b/sbin/mount_std/mount_fdesc.8 @@ -0,0 +1,171 @@ +.\" +.\" 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. |