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Command: fd | Section: 4 | Source: OpenBSD | File: fd.4
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
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
tty(4)
FreeBSD 14.1-RELEASE-p8 May 31, 2007 FreeBSD 14.1-RELEASE-p8