.\" .\" 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.