.TH DUP 3 
.SH NAME
dup \- dups of open files
.SH SYNOPSIS
.nf
.B bind #d /fd

.B /fd/0
.B /fd/1
\&...
.fi
.SH DESCRIPTION
The
.I dup
device serves a one-level directory containing files whose
names are decimal numbers.
A file of name
.I n
corresponds to open file descriptor
.I n
in the current process.
.PP
An
.IR open (5)
of file
.I n
results in a file descriptor identical to
what would be returned from a
.IB dup ( n ", -1)"
system call.
Note that the result is no longer a file in the
.I dup
device.
.PP
The
.I stat
operation returns information about the device file, not the open file it points to.
A stat of
.BI #d/ n
will contain
.I n
for the name, 0 for the length, and 0400, 0200, or 0600
for the mode, depending on whether the dup target is open
for reading, writing, or both.
.SH SEE ALSO
.IR dup (2)