CONS(3) 						     Library Functions Manual							   CONS(3)

NAME

       cons  -	console, clocks, process/process group ids, user, null, klog, stats, lights, noise, sysstat, hz, swap, key, hostowner, hostdomain,
       authenticate, authcheck, authenticator

SYNOPSIS

       bind #c /dev

       /dev/authcheck
       /dev/authenticate
       /dev/authenticator
       /dev/clock
       /dev/cons
       /dev/consctl
       /dev/cputime
       /dev/hostdomain
       /dev/hostowner
       /dev/hz
       /dev/key
       /dev/klog
       /dev/lights
       /dev/msec
       /dev/noise
       /dev/null
       /dev/pgrpid
       /dev/pid
       /dev/ppid
       /dev/swap
       /dev/sysname
       /dev/sysstat
       /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 keyboard.	Normally, characters are buffered to enable erase and kill processing.	 A
       control-U, typed at the keyboard 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.  Characters 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 them into the buffer.  A read(2) of length greater	than  zero
       causes the process to wait until a newline or a 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 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 and are not treated specially, and characters are available to read as soon as they are typed.  Ordinary mode is reen-
       tered 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.

       The null file throws away anything written to it and always returns zero bytes when read.

       The klog file contains the tail of messages written by kernel logging statements.

       Writing a number (as plain text) to the lights device directs any lights that are available to turn on and off.	The bits of the number are
       mapped to the lights in a processor-dependent way.

       Writing two blank- or tab-separated numbers to the noise device causes the machine to make a tone, if possible.	The first  number  is  the
       frequency, in Hertz, and the second is the duration, in milliseconds.

       The  hostdomain	file  contains	the  name  of  the  authentication  domain that this host belongs to; see auth(6).  Only the user named in
       /dev/hostowner may write this.

       The hostowner file contains the name of the user that owns the console device files.  The hostowner also  has  group  permissions  for  any
       local devices.

       The  key  file  is used to set the DES key used for encryption.	Each machine has one key.  Only the user named in /dev/hostowner may write
       this.

       The authenticate file is used to authenticate new users to the kernel; see auth(6).  After an open, the first read returns a ticket request
       message of the following form:
	    char num;
	    char authid[28];
	    char authdom[48];
	    char chal[8];
	    char hostid[28];
	    char uid[28];
       Here  num is 1, authid and hostid are the contents of hostowner, and authdom is the contents of hostdomain.  Chal is an 8 byte random chal-
       lenge created by the kernel.  A subsequent write of a valid ticket encrypted with the key contained in key changes the  user  name  of  the
       writing process to the value of suid in the ticket.  The ticket is of the form:
	    char num;
	    char chal[8];
	    char cuid[28];
	    char suid[28];
	    char noncekey[7];
       The  ticket  is	valid if num is 64 and chal matches the challenge in the ticket request.  Writing an invalid ticket generates an error.  A
       read following a successful write yields an authenticator message of the form:
	    char num;
	    char chal[8];
	    char id[4];
       The authenticator is encrypted in noncekey from the ticket.  Num is 66, id[0-4] are 0, and chal	matches  the  challenge  in  the  original
       ticket request.

       The  authenticator  file  is used to generate an authenticator from a ticket.  One writes a ticket encrypted with the key contained in key,
       followed, optionally, by a 4-byte id; a missing id defaults to zero.  If the client uid matches the current user, a subsequent read  yields
       an authenticator for that ticket with the given id.

       The authcheck file is used to match authenticators to tickets.  A write of an authenticator appended to the end of a ticket succeeds if the
       ticket is encrypted with the key contained in key, the ticket's num is 65, the authenticator is encrypted with the ticket's  noncekey,  the
       authenticator's	and  ticket's  chal's match, the authenticator's num is 66, and the authenticator's id is 0.  Alternatively, the write may
       consist of ticket, authenticator, chal, and id, in which case the given chal and id must match those of the authenticator.

       The user file contains the name of the user associated with the current process.  Any process can change to user none by  writing  none	to
       this file.

       The  rest  of  the files contain (mostly) read-only strings.  Each string has a fixed length: a 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  cputime  file holds 6 numbers, containing the time in milliseconds that the current process has spent in user mode, system calls, real
       elapsed time, and then the time spent, by exited children and their descendants, in user mode, system calls, and real elapsed time.

       The clock file holds two numbers: the number of clock ticks since booting followed by the number of clock ticks in a second.

       The sysname file holds the textual name of the machine, e.g.  kremvax, if known.

       The sysstat file holds 8 numbers: processor number, context switches, interrupts, system calls, page faults, tlb faults,  tlb  purges,  and
       load  average.	The  load  average is in units of milli-CPUs and is decayed over time; the others are total counts from boot time.  If the
       machine is a multiprocessor, sysstat holds one line per processor.  Writing anything to sysstat resets all of the counts on all processors.

       The swap device holds a string of the form

	      m1/m2 memory s1/s2 swap

       These give, for each of internal memory and the swapping area, the number of pages used and the total available.   These  numbers  are  not
       blank padded.  To turn on swapping, write to swap the textual file descriptor number of a file or device on which to swap.  See swap(8).

       The other files served by the cons device are all single numbers:

       hz	 frequency of the system clock

       msec	 number of milliseconds since booting

       pgrpid	 process group number

       pid	 process number

       ppid	 parent's process number

       time	 number of seconds since the epoch 00:00:00 GMT, Jan. 1, 1970.	(Can be written once, to set at boot time.)

SEE ALSO

       bit(3), keyboard(6), auth(6), utf(6), swap(8)

SOURCE

       /sys/src/9/port/devcons.c

BUGS

       For debugging, two control-T's followed by a letter generate console output: prints data about processes, prints data about streams, prints
       data about the mount device, prints data about the bitblt device, and prints data about kernel memory allocation.

       The system can be rebooted by typing

																	   CONS(3)