MOUNT_FDESC(8) | System Manager's Manual | MOUNT_FDESC(8) |
mount_fdesc
—
mount_fdesc |
[-o options]
fdesc mount_point |
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. The directory specified by
mount_point is converted to an absolute path before use.
This command is normally executed by mount(8) at boot time.
The options are as follows:
-o
-o
flag followed by a
comma separated string of options. See the
mount(8) man page for
possible options 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 existing 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 controlling terminal. It appears as a named pipe (FIFO) but behaves in exactly the same way as the real controlling terminal device.
mount_fdesc
utility first appeared in
4.4BSD.
December 29, 2013 | NetBSD 9.4 |