Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
fdesc(5)		    BSD	File Formats Manual		      fdesc(5)

NAME
     fdesc -- file-descriptor file system

SYNOPSIS
     fdesc     /dev fdesc rw 0 0

DESCRIPTION
     The file-descriptor file system, or fdesc,	provides access	to the per-
     process file descriptor namespace in 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 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 exist-
     ing 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 equiva-
     lent 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 con-
     trolling terminal.	 It appears as a named pipe (FIFO) but behaves in ex-
     actly the same way	as the real controlling	terminal device.

FILES
     /dev/fd/#
     /dev/stdin
     /dev/stdout
     /dev/stderr
     /dev/tty

SEE ALSO
     tty(4), mount_devfs(8), mount_fdesc(8)

HISTORY
     The fdesc filesystem first	appeared in 4.4BSD. The	fdesc manual page
     first appeared in FreeBSD 2.2.

AUTHORS
     The fdesc manual page was written by Mike Pritchard <mpp@FreeBSD.org>,
     and was based on the mount_fdesc(8) manual	page written by
     Jan-Simon Pendry.

4.4BSD			       December	14, 1996			4.4BSD

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

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=fdesc&sektion=5&manpath=FreeBSD+3.2-RELEASE>

home | help