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FD(4)		       FreeBSD Kernel Interfaces Manual			 FD(4)

NAME
     fd, stdin,	stdout,	stderr -- file descriptor files

DESCRIPTION
     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 ex-
     isting descriptor,	the call:

	   fd =	open("/dev/fd/0", mode);

     and the call:

	   fd =	fcntl(0, F_DUPFD, 0);

     are equivalent.

     Opening the files /dev/stdin, /dev/stdout and /dev/stderr 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.

IMPLEMENTATION NOTES
     By	default, /dev/fd is provided by	devfs(5), which	provides nodes for the
     first three file descriptors.  Some sites may require nodes for addi-
     tional file descriptors; these can	be made	available by mounting
     fdescfs(5)	on /dev/fd.

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

SEE ALSO
     tty(4), devfs(5), fdescfs(5)

FreeBSD	13.0			 June 9, 1993			  FreeBSD 13.0
NAME | DESCRIPTION | IMPLEMENTATION NOTES | FILES | SEE ALSO

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