CONS(3) CONS(3)
NAME
cons - console device
SYNOPSIS
bind #c /dev
/dev/cons
/dev/consctl
/dev/drivers
/dev/jit
/dev/keyboard
/dev/klog
/dev/kprint
/dev/memory
/dev/msec
/dev/null
/dev/notquiterandom
/dev/pgrpid
/dev/pin
/dev/pointer
/dev/random
/dev/sysname
/dev/time
/dev/user
DESCRIPTION
The console device serves a one-level directory giving
access to the console and miscellaneous information.
Reading the cons file returns characters typed on the key-
board. Normally, characters are buffered to enable erase
and kill processing. A control-U, `^U', typed at the key-
board kills the current input line (removes all characters
from the buffer of characters not yet read via cons), and a
backspace erases the previous non-kill, non-erase character
from the input buffer. Killing and erasing only delete
characters back to, but not including, the last newline.
Typed keystrokes produce 16-bit characters that are trans-
lated into the variable-length UTF encoding (see utf(6))
before putting them into the buffer. A read of 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. A single line containing a
`^D' can be used as an end of file indication to programs
that take interactive input.
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CONS(3) CONS(3)
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 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 to cons causes the characters to be printed on the
console screen.
The keyboard file returns the underlying tokens produced by
the keyboard hardware as they are produced; in the emulation
environment, it is like an always-raw cons file.
The null file throws away anything written to it and always
returns zero bytes when read.
The klog file returns the tail of messages written by kernel
logging statements.
The kprint file returns console output: messages written by
kernel print statements and messages written by processes to
this driver's cons file. Until kprint is opened, system
console output is handled normally. Once kprint has been
opened, if the machine's console is a serial line, the data
is sent both to the serial console and to kprint; if the
console is a graphics screen, the data is sent only to
kprint.
A read of the pointer file returns the status of the mouse
or other pointing device: its position and button state.
The read blocks until the state has changed since the last
read. The read returns an m character followed by three
integers in the standard Inferno 12-character decimal for-
mat: right-adjusted numerals with leading blanks to fill the
field to 11 characters, followed by a blank. The integers
are the device's coordinates on the screen and a bit mask
with the 1, 2, and 4 bits when the pointer's left, middle,
and right buttons, respectively, are down.
The pin file, when read, returns either the string no pin if
no PIN has been set for authentication, or pin set if one
has. The pin file may be written once with a decimal repre-
sentation of the PIN to use on this Inferno machine.
The random device returns as many bytes of random data as
are requested in the read.
The notquiterandom device returns as many bytes of pseudo-
random data as are requested in the read; this is typically
faster than random but the results are more predictable.
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The rest of the files contain (mostly) read-only strings.
Each string has a fixed length: a read (see sys-read(2)) of
more than that gives a result of that fixed length (the
result does not include a terminating zero byte); a read of
less than that length leaves the file offset so the rest of
the string (but no more) will be read the next time. To
reread the file without closing it, seek must be used to
reset the offset. When the file contains numeric data, each
number is formatted in decimal as an 11-digit number with
leading blanks and one trailing blank: twelve bytes total.
The sysname file holds the textual name of the machine.
The user file contains the name of the user associated with
the current process.
The memory file returns a formatted presentation of the
state of the memory allocation pools in the system. Each
line of output returned reports, for a single pool, the
amount of memory in use, the upper size limit, the number of
allocations done, the number of frees done, the number of
extensions done, and the name of the pool.
The drivers file returns a list of the device drivers loaded
in the system. Each line gives the name of the device for
bind(1), such as #c, followed by the name of the driver as
used in the system configuration file.
The other files served by the cons device are all single
numbers:
jit non-zero if `just in time' compilation is configured
(can be written to change the state).
msec the value of a millisecond counter
time number of microseconds since the epoch 00:00:00 GMT,
Jan. 1, 1970. (Can be written once, to set at boot
time.)
SOURCE
/emu/devcon.c
/os/port/devcons.c
SEE ALSO
draw(3), keyboard(6), utf(6)
BUGS
For debugging, on native systems only, two control-T's fol-
lowed by a letter generate console output: `^T^Tp' prints
data about kernel processes, `^T^Ts' prints the kernel
stack, `^T^Tx' prints data about memory allocation.
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The system can be rebooted by typing `^T^Tr'.
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