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FDESCFS(5)                FreeBSD File Formats Manual               FDESCFS(5)

NAME
     fdescfs - file-descriptor file system

SYNOPSIS
     fdescfs /dev/fd fdescfs rw 0 0

DESCRIPTION
     The file-descriptor file system, or fdescfs, provides access to the per-
     process file descriptor namespace in the global file system namespace.
     The conventional mount point is /dev/fd.

     The file system's 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.

     Flags to the open(2) call other than O_RDONLY, O_WRONLY and O_RDWR are
     ignored.

     Note: /dev/fd/0, /dev/fd/1 and /dev/fd/2 files are created by default
     when devfs alone is mounted.  fdescfs creates entries for all file
     descriptors opened by the process.

FILES
     /dev/fd/#

EXAMPLES
     To mount a fdescfs volume located on /dev/fd:

           mount -t fdescfs null /dev/fd

SEE ALSO
     devfs(5), mount(8)

HISTORY
     The fdescfs file system first appeared in 4.4BSD.  The fdescfs manual
     page first appeared in FreeBSD 2.2.

AUTHORS
     The fdescfs manual page was written by Mike Pritchard <mpp@FreeBSD.org>,
     and was based on the manual page written by Jan-Simon Pendry.

FreeBSD 11.0-PRERELEASE       September 18, 2010       FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | FILES | EXAMPLES | SEE ALSO | HISTORY | AUTHORS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=fdescfs&manpath=FreeBSD+9.2-RELEASE>

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