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FD(4)                     OpenBSD Programmer's 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)

OpenBSD 5.4                      May 31, 2007                      OpenBSD 5.4

NAME | DESCRIPTION | FILES | SEE ALSO