DUP(3) DUP(3)
NAME
dup - dups of open files
SYNOPSIS
bind #d /fd
/fd/0
/fd/0ctl
/fd/1
/fd/1ctl
...
DESCRIPTION
The dup device serves a one-level directory containing files
whose names are decimal numbers. Each such file also has an
associated control file. A file of name n corresponds to
open file descriptor n in the current process.
A sys-open(2) of file n results in a file descriptor identi-
cal to what would be returned from a system call sys->dup(n,
-1). Note that the result is no longer a file in the dup
device.
The stat operation returns information about the device
file, not the open file it points to. A stat of #d/n will
contain n for the name, 0 for the length, and 400, 200, or
600 (octal) for the mode, depending on whether the dup tar-
get is open for reading, writing, or both.
A file of name nctl may be read to discover the properties
of the associated file descriptor, in format identical to
that of the fd file in prog(3).
SEE ALSO
sys-dup(2)
SOURCE
/usr/inferno/emu/port/devdup.c
/usr/inferno/os/port/devdup.c