MOUNT_FDESC(8) BSD System Manager's Manual MOUNT_FDESC(8)
mount_fdesc - mount the file-descriptor file system
mount_fdesc [-o options] fdesc mount_point
The mount_fdesc command attaches an instance of the per-process file descriptor namespace to the global filesystem namespace. The conventional mount point is /dev and the filesystem should be union mounted in order to augment, rather than replace, the existing entries in /dev. This com- mand is invoked by mount(8) when using the syntax mount [options] -t fdesc fdesc mount_point This command is normally executed by mount(8) at boot time. The options are as follows: -o options Options are specified with a -o flag followed by a comma separat- ed string of options. See the mount(8) man page for possible op- tions and their meanings. The contents of the mount point are fd, stderr, stdin, stdout and tty. 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 /dev/fd/0 through /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 exist- ing descriptor, the call: fd = open("/dev/fd/0", mode); and the call: fd = fcntl(0, F_DUPFD, 0); are equivalent. The files /dev/stdin, /dev/stdout and /dev/stderr appear as symlinks to the relevant entry in the /dev/fd sub-directory. Opening them is equivalent to the following calls: fd = fcntl(STDIN_FILENO, F_DUPFD, 0); fd = fcntl(STDOUT_FILENO, F_DUPFD, 0); fd = fcntl(STDERR_FILENO, F_DUPFD, 0); Flags to the open(2) call other than O_RDONLY, O_WRONLY and O_RDWR are ignored. The /dev/tty entry is an indirect reference to the current process's con- trolling terminal. It appears as a named pipe (FIFO) but behaves in ex- actly the same way as the real controlling terminal device.
/dev/fd/# /dev/stdin /dev/stdout /dev/stderr /dev/tty
mount(2), tty(4), fstab(5), mount(8), umount(8)
The mount_fdesc utility first appeared in 4.4BSD.
This filesystem may not be NFS-exported. MirOS BSD #10-current March 27, 1994 1
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