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NAME    [Toc]    [Back]

     mount_fdesc - mount the file-descriptor file system

SYNOPSIS    [Toc]    [Back]

     mount_fdesc [-o options] fdesc mount_point

DESCRIPTION    [Toc]    [Back]

     The mount_fdesc command attaches an instance of the per-process file descriptor
  namespace to the global filesystem namespace.  The
     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 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 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

     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.

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

     mount(2), tty(4), fstab(5), mount(8), umount(8)

HISTORY    [Toc]    [Back]

     The mount_fdesc utility first appeared in 4.4BSD.

CAVEATS    [Toc]    [Back]

     This filesystem may not be NFS-exported.

OpenBSD      3.6                          March      27,     1994
[ Back ]
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