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

     fdescfs - file-descriptor file system

     fdescfs /dev/fd fdescfs rw 0 0

     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

     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.


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

           mount -t fdescfs null /dev/fd

     devfs(5), mount(8)

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

     The fdescfs manual page was written by Mike Pritchard <[email protected]>,
     and was based on the manual page written by Jan-Simon Pendry.

FreeBSD 11.1-RELEASE-p4       September 18, 2010       FreeBSD 11.1-RELEASE-p4
Command Section