FD(4) - Device Drivers Manual #
FD(4) - Device Drivers Manual
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 existing 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.
These devices may not be opened by processes which are tainted
as a result of setuid or setgid behaviours, as documented in
issetugid(2).
In those cases, an error return will occur with
errno
set to
EPERM.
FILES #
/dev/fd/#
/dev/stdin
/dev/stdout
/dev/stderr
SEE ALSO #
OpenBSD 7.5 - May 31, 2007