KBDFS(8) KBDFS(8)
NAME
kbdfs, console - keyboard and console filesystem
SYNOPSIS
aux/kbdfs [ -Dd ] [ -s srv ] [ -m mntpnt ] [ consfile ]
mount -b /srv/cons /dev
/dev/cons
/dev/consctl
/dev/kbd
/dev/kbdin
/dev/kbin
/dev/kbmap
console [ cmd args... ]
DESCRIPTION
Started on boot(8), kbdfs translates raw keyboard scancodes
from /dev/scancode (see kbd(3)) and its kbin and kbdin file
and optionally reads console input from consfile to provide
initial keyboard and console input.
It serves a one-level directory containing the files cons,
consctl, kbd, kbdin, kbin and kbmap.
The -D flag enables a debug trace of 9p messages and -d pre-
vents kbdfs from making its memory private.
The -s option causes kbdfs to post its channel on /srv/srv.
On system startup, boot(8) sets this to cons. With the -m
option, kbdfs mounts itself on mntpnt (see bind(2)), other-
wise on /dev (the default).
The console command executes cmd (defaults to the system
shell) under its own kbdfs instance providing a serial con-
sole if $console environment variable is set.
Console
Reading the cons file returns characters typed on the con-
sole. Normally, characters are buffered to enable erase and
kill processing. A control-U, `^U', typed at the keyboard
erases the current input line (removes all characters from
the buffer of characters not yet read via cons), and a back-
space erases the previous non-kill, non-erase character from
the input buffer. The combination control-W, `^W', deletes
the input last word. Killing and erasing only delete char-
acters back to, but not including, the last newline. Char-
acters typed at the keyboard actually produce 16-bit runes
(see utf(6)), but the runes are translated into the
variable-length UTF encoding (see utf(6)) before putting
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them into the buffer. A read(2) of a length greater than
zero causes the process to wait until a newline or a `^D'
ends the buffer, and then returns as much of the buffer as
the argument to read allows, but only up to one complete
line. A terminating `^D' is not put into the buffer. If
part of the line remains, the next read will return bytes
from that remainder and not part of any new line that has
been typed since.
If the string rawon has been written to the consctl file and
the file is still open, cons is in raw mode: characters are
not echoed as they are typed, backspace, `^U,' `^W' and `^D'
are not treated specially, and characters are available to
read as soon as they are typed. Ordinary mode is reentered
when rawoff is written to consctl or this file is closed.
A write (see read(2)) to cons causes the characters to be
printed on the console screen.
When a consfile is passed to kbdfs(8) as its last argument,
it reads and processes the characters from that file and
forwards them to the cons file with the same text processing
applied as on keyboard input. This is used to provide a
serial console when $console environment variable is set.
(see plan9.ini(8)).
Keyboard
A read on the kbd file returns the character k, K or c fol-
lowed by a null terminated, variable-length, UTF encoded
string. The k message is sent when a key is pressed down and
K when a key is released. The following string contains all
the keycodes of the keys that are currently pressed down in
unshifted form. This includes all keys that have a keyboard
mapping and modifier keys. The string following the c mes-
sage contains the single character that would have been
returned on the cons file instead. The c message will be
resent at the keyboard repeat rate. A single read(2) can
return multiple concatenated messages at once (delimited by
the null byte) or block when there are no messages queued.
Opening the kbd file disables input processing on the cons
file until it is closed again.
K, k and c messages can be written to kbdin and will for-
warded to the reader of cons or kbd. Writing a r or R mes-
sage followed by a UTF encoded rune will simulate the press
or release of that particular rune.
Raw scancodes can be written to the kbin file for external
keyboard input (used for USB keyboards).
Keyboard map
Scancodes are mapped to Unicode characters with a number of
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translation tables. These tables can be accessed with the
kbmap file.
Reads return the current contents of the map. Each entry is
one line containing three 11 character numeric fields, each
followed by a space: a table number, an index into the table
(scan code), and the decimal value of the corresponding Uni-
code character (0 if none). The table numbers are platform
dependent; they typically distinguish between unshifted and
shifted keys. The scan code values are hardware dependent
and can vary from keyboard to keyboard.
Writes to the file change the map. Lines written to the
file must contain three space-separated fields, representing
the table number, scan code index, and Unicode character.
Values are taken to be decimal unless they start with 0x
(hexadecimal) or 0 (octal). The Unicode character can also
be represented as 'x where x gives the UTF-8 representation
of the character (see utf(6)), or as ^X to represent a con-
trol character.
SEE ALSO
cons(3), keyboard(6), utf(6), kbd(3), plan9.ini(8)
FILES
/sys/lib/kbmap/*
SOURCE
/sys/src/cmd/aux/kbdfs
/rc/bin/console
HISTORY
Kbdfs first appeared in 9front (May, 2011).
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