fd4

Overview

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