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Plan 9 - man page for cons (plan9 section 3)

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CONS(3) 										  CONS(3)

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

       bind #c /dev


       The console device serves a one-level directory giving access to the console and miscella-
       neous 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 buf-
       fer 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 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.

       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 avail-
       able 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 con-
       tents of hostdomain.  Chal is an 8 byte random challenge created by the kernel.	A  subse-
       quent  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
	    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 authentica-
       tor appended to the end of a ticket succeeds if the ticket is encrypted with the key  con-
       tained  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, authen-
       ticator, chal, and id, in which case the given chal and id must match those of the authen-

       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

       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 any-
       thing 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

       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.)

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


       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

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