59 lines
1.1 KiB
Plaintext
59 lines
1.1 KiB
Plaintext
|
.TH DUP 3
|
||
|
|
.SH NAME
|
||
|
|
dup \- dups of open files
|
||
|
|
.SH SYNOPSIS
|
||
|
|
.nf
|
||
|
|
.B bind #d /fd
|
||
|
|
|
||
|
|
.B /fd/0
|
||
|
|
.B /fd/0ctl
|
||
|
|
.B /fd/1
|
||
|
|
.B /fd/1ctl
|
||
|
|
\&...
|
||
|
|
.fi
|
||
|
|
.SH DESCRIPTION
|
||
|
|
The
|
||
|
|
.I 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
|
||
|
|
.I n
|
||
|
|
corresponds to open file descriptor
|
||
|
|
.I n
|
||
|
|
in the current process.
|
||
|
|
.PP
|
||
|
|
An
|
||
|
|
.IR open (2)
|
||
|
|
of file
|
||
|
|
.I n
|
||
|
|
results in a file descriptor identical to
|
||
|
|
what would be returned from a system call
|
||
|
|
.IB dup ( n ,
|
||
|
|
.BR -1) .
|
||
|
|
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.
|
||
|
|
.PP
|
||
|
|
A file of name
|
||
|
|
.IB n ctl
|
||
|
|
may be read to discover the properties of the associated file descriptor, in format identical to that of the
|
||
|
|
.B fd
|
||
|
|
file in
|
||
|
|
.IR proc (3).
|
||
|
|
.SH SEE ALSO
|
||
|
|
.IR dup (2)
|
||
|
|
.SH SOURCE
|
||
|
|
.B /sys/src/9/port/devdup.c
|