Mac Developer Library Developer


This manual page is for Mac OS X version 10.9

If you are running a different version of Mac OS X, view the documentation locally:

  • In Terminal, using the man(1) command

Reading manual pages

Manual pages are intended as a quick reference for people who already understand a technology.

  • To learn how the manual is organized or to learn about command syntax, read the manual page for manpages(5).

  • For more information about this technology, look for other documentation in the Apple Developer Library.

  • For general information about writing shell scripts, read Shell Scripting Primer.

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 command is normally exe-cuted executed
     cuted by mount(8) at boot time.

     The options are as follows:

     -o      Options are specified with a -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/_ 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(2), unmount(2), tty(4), fstab(5), mount(8)

     No ~.  and .. entries appear when listing the contents of the /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 ~.  and .. in a pathname.

     This filesystem may not be NFS-exported.

     The mount_fdesc utility first appeared in 4.4BSD.

4.4BSD                          March 27, 1994                          4.4BSD

Reporting Problems

The way to report a problem with this manual page depends on the type of problem:

Content errors
Report errors in the content of this documentation with the feedback links below.
Bug reports
Report bugs in the functionality of the described tool or API through Bug Reporter.
Formatting problems
Report formatting mistakes in the online version of these pages with the feedback links below.