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.
An
open(2)
of file
n
results in a file descriptor identical to
what would be returned from a system call
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 0400, 0200, or 0600
for the mode, depending on whether the dup target 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
proc(3).
SEE
dup(2)
SOURCE
/sys/src/9/port/devdup.c