shithub: 9ferno

ref: 6966e8d72ae8fb72ebf98909acbd464aff84a3cc

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.TH CONS 3 
.SH NAME
cons \- console device
.SH SYNOPSIS
.nf
.B bind #c /dev

.B /dev/cons
.B /dev/consctl
.B /dev/drivers
.B /dev/jit
.B /dev/keyboard
.B /dev/klog
.B /dev/kprint
.B /dev/memory
.B /dev/msec
.B /dev/null
.B /dev/notquiterandom
.B /dev/pointer
.B /dev/random
.B /dev/scancode
.B /dev/sysctl
.B /dev/sysname
.B /dev/time
.B /dev/user
.fi
.SH DESCRIPTION
The console device serves a one-level directory
giving access to the console and
miscellaneous information.
.PP
Reading the
.B cons
file returns characters typed on the keyboard.
Normally, characters are buffered to enable erase and kill processing.
A control-U,
.LR ^U ,
typed at the keyboard
.I kills
the current input line (removes all characters
from the buffer of characters
not yet read via
.BR cons ),
and a backspace
.I 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 21-bit runes
that are translated into the variable-length
.SM UTF
encoding (see
.IR utf (6))
before putting them into the buffer.
A
.B read
of length greater than zero causes the process to wait until a
newline or a
.L ^D
ends the buffer, and then returns as much of the buffer as the argument
to
.B read
allows, but only up to one complete line.
A terminating
.L ^D
is not put into the buffer.
If part of the line remains, the next
.B read
will return bytes from that remainder and not part of any new line
that has been typed since. A single line containing a
.L ^D
can be used as an end of file indication to programs that take interactive input.
.PP
If
the string
.B rawon
has been written to the
.B consctl
file and the file is still open,
.B cons
is in
.IR "raw mode" :
characters are not echoed as they are typed,
backspace,
.L ^U
and
.L ^D
are not treated specially,
and characters are available to
.B read
as soon as they are typed.
Ordinary mode is reentered when
.B rawoff
is written to
.B consctl
or this file is closed.
.PP
A
.B write
to
.B cons
causes the characters to be printed on the console screen.
.PP
The
.B 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
.B cons
file.
.PP
The
.B null
file throws away anything written to it
and always returns zero bytes when read.
.PP
The
.B klog
file
returns the tail of messages written by the native kernel debugging function
.B kprint
(mainly used when debugging interrupt handlers in device drivers).
It is available only in native kernel implementations.
.PP
The
.B kprint
file
returns console output: messages written by kernel print statements and messages
written by processes to this driver's
.B cons
file.
Until
.B kprint
is opened, system console output is handled normally.
Once
.B kprint
has been opened,
if the machine's console is a serial line, the data is sent both to
the serial console and to
.BR kprint ;
if the console is a graphics screen, the data is sent only to
.BR kprint .
.PP
A read of the
.B 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 49 bytes: the letter
.B m
followed by four fields containing decimal integers, each 11 characters wide followed by a blank.
The integers are: x and y,
coordinates of the pointer on the screen; a bit mask with the
1, 2, and 4 bits when the pointer's left, middle, and right
buttons, respectively, are down; and a time stamp in units of milliseconds.
.PP
Writing to the
.B pointer
file, using the same format,
causes the pointer to move to the specified x, y position
(the button and millisecond fields are ignored, and optional).
If there is a visible image representing the pointer's position,
that will move too.
.PP
The
.B random
device returns as many bytes of random data as are requested in the
.BR read .
.PP
The
.B notquiterandom
device returns as many bytes of pseudo-random data as are requested in the
.BR read ;
this is typically faster than
.B random
but the results are more predictable.
.PP
The
.B scancode
device provides access to the raw scan codes of the primary
.B keyboard .
While it is open, key strokes are diverted from
.B cons
and
.B keyboard .
The first
.IR read (2)
after opening returns an identifier string which defines the format of data delivered
by subsequent
reads. Known ones are defined in
.IR scancode (6).
The most common format is a single byte per scan code, where the top bit is 1 for
up and 0 for down, and the bottom 7 bits are the scan code. Some input devices
have a larger scan code space; in this case scan codes are often delivered as two byte
little endian quantities, where the top bit is the up/down signifier, and the bottom
15 bits are the scan code. In all cases the meaning of the individual scan codes is
device specific.
.PP
The rest of the files contain (mostly) read-only strings.
Each string has a fixed length: a
.I read
(see
.IR sys-read (2))
of more than that gives a result of that fixed length (the result does not
include a terminating zero byte);
a
.I 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,
.I 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.
.PP
The
.B sysctl
file can be read to return the current Inferno version. Writing the string
.B reboot
to it attempts to reboot the system, writing
.B halt
attempts to halt the system. Writing
.B nobroken
ensures that broken processes have all associated memory freed before
being destroyed,
writing
.B broken
ensures that they are left in this state to allow debugging (the default).
Only the privileged user is allowed to write to this file.
.PP
The
.B sysname
file holds the textual name of the machine.
It can only be written by the privileged user.
.PP
The
.B user
file contains the name of the user associated with the current process.
It can only be written by the privileged user. In the emulation environment,
writing to this file also attempts to set the user id in the host operating
system to the specified value.
.PP
The
.B 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 high water mark,
the number of allocations done,
the number of frees done,
the number of extensions done,
the largest chunk available
and the name of the pool.
.PP
The
.B drivers
file returns a list of the device drivers loaded in the system.
Each line gives the name of the device for
.IR bind (1),
such as
.BR #c ,
followed by the name of the driver as used in the system configuration file.
.PP
The other files served by the
.I cons
device are all single numbers:
.TP
.B jit
non-zero if `just in time' compilation is configured (can be written to change the state). Writing 0 turns off JIT compilation, 1 turns it on and larger values give increasingly
detailed traces of the compilation for debugging purposes.
.TP
.B msec
the value of a millisecond counter
.TP
.B time
number of microseconds since the epoch 00:00:00 GMT, Jan. 1, 1970.
(Can be written once by the privileged user, to set at boot time.)
.SH SOURCE
.B /emu/port/devcons.c
.br
.B /os/port/devcons.c
.SH SEE ALSO
.IR draw (3),
.IR keyboard (6),
.IR utf (6),
.IR eve (10.2)
.SH BUGS
For debugging, on native systems only,
two control-T's followed by a letter
generate console output:
.L ^T^Tp
prints data about kernel processes,
.L ^T^Ts
prints the kernel stack,
.L ^T^Tx
prints data about memory allocation.
.PP
The system can be rebooted by typing
.LR ^T^Tr .