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