glenda.party
term% ls -F
term% pwd
$home/manuals/9front/3/cons
term% cat index.txt
CONS(3)                    Library Functions Manual                    CONS(3)



NAME
       cons  - console, clocks, process/process group ids, user, null, reboot,
       etc.

SYNOPSIS
       bind #c /dev

       /dev/bintime
       /dev/config
       /dev/cons
       /dev/cputime
       /dev/drivers
       /dev/hostdomain
       /dev/hostowner
       /dev/kmesg
       /dev/kprint
       /dev/mordor
       /dev/null
       /dev/osversion
       /dev/pgrpid
       /dev/pid
       /dev/ppid
       /dev/random
       /dev/reboot
       /dev/swap
       /dev/sysname
       /dev/sysstat
       /dev/time
       /dev/user
       /dev/zero

DESCRIPTION
       The console device serves a one-level directory giving  access  to  the
       console screen and miscellaneous information.

       A  write  (see  read(2)) to cons causes the characters to be printed on
       the console screen. Console input is handled  by  a  different  program
       (see kbdfs(8)).

       The  osversion  file contains a textual representation of the operating
       system's version and parameters.  At the moment, it contains one field:
       the 9P protocol version, currently 2000.

       The  config  file contains a copy of the kernel configuration file used
       to build the kernel.

       The kmesg file holds the last 16 kilobytes of  output  written  to  the
       console  by  the  kernel's  print statements or by processes writing to
       /dev/cons.  It is useful for retrieving boot  messages  once  the  boot
       process is over.

       The  kprint  file  may be read to receive a copy of the data written to
       the console by the kernel's print statements or by processes writing to
       /dev/cons.   Only  data  written after the file is opened is available.
       If the machine's console is a serial line, the data is sent both to the
       console and to kprint; if its console is a graphics screen, the data is
       sent either to the display or to kprint, but not both.  (It  is  advis‐
       able not to open kprint on terminals until you have started rio(1).)

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

       The zero file is a read-only file that produces an infinite  stream  of
       zero-valued bytes when read.

       The  drivers file contains, one per line, a listing of the drivers con‐
       figured in the kernel, in the format

              #c cons

       The hostdomain file contains the name of the authentication domain that
       this host belongs to; see authsrv(6).  Only the user named in /dev/hos‐
       towner 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.

       Reads from random return a stream of random numbers.  The  numbers  are
       generated  by  a  low priority kernel process that loops incrementing a
       variable.  Each clock tick the variable  is  sampled  and,  if  it  has
       changed sufficiently, the last few bits are appended to a buffer.  This
       process is inefficient at best producing at most a few hundred  bits  a
       second.  Therefore, random should be treated as a seed to pseudo-random
       number generators which can produce a faster rate stream.

       Writing the string reboot to reboot causes the system to shutdown  and,
       if  possible,  restart.  Writing the string reboot kernelpath loads the
       named kernel image and restarts, preserving the kernel configuration in
       #ec,  except  that the bootfile variable is set to kernelpath.  Writing
       the string rdb activates the remote  kernel  debugger  (see  rdbfs(4)).
       Only the host owner has the ability to open this file.

       Bintime  is  a  binary  interface that provides the same information as
       time (q.v.), in binary form, and  also  controls  clock  frequency  and
       clock  trim.   All integers read or written from bintime are in big en‐
       dian order.  Unlike the other files, reads and writes do not affect the
       offset.   Therefore,  there  is no need for a seek back to zero between
       subsequent accesses.  A read of bintime returns 24 bytes, three 8  byte
       numbers,  representing  nanoseconds  since start of epoch, clock ticks,
       and clock frequency.

       A write to bintime is a message with one of 3 formats:

       n<8-byte time>
                   set the nanoseconds since epoch to the given time.

       d<8-byte delta><4-byte period>
                   trim the nanoseconds since epoch by delta over the next pe‐
                   riod seconds.

       f<8-byte freq>
                   Set  the  frequency for interpreting clock ticks to be freq
                   ticks per second.

       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.  If the
       binary  number  fits in 32 bits, it is formatted as an 11 digit decimal
       number with leading blanks and one trailing blank; totaling  12  bytes.
       Otherwise,  it  is  formatted  as 21 digit decimal numbers with leading
       blanks and one trailing blank; totaling 22 bytes.

       The cputime file holds six 32-bit numbers, containing the time in  mil‐
       liseconds  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 time file holds one 32-bit number representing  the  seconds  since
       start of epoch and three 64-bit numbers, representing nanoseconds since
       start of epoch, clock ticks, and clock frequency.

       A write of a decimal number to time will set the seconds since epoch.

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

       The  sysstat file holds 10 numbers: processor number, context switches,
       interrupts, system calls, page faults, TLB faults, TLB purges, load av‐
       erage, idle time and time spent servicing interrupts.  The load average
       is in units of milli-CPUs and is decayed over time; idle time  and  in‐
       terrupt  time  are  percentage  units; 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 text block giving memory usage statistics:

              n memory
              n pagesize
              n kernel
              n/m user
              n/m swap
              a/n/m kernel malloc
              a/n/m kernel draw

       These are total memory (bytes), system page size (bytes), kernel memory
       (pages),  user memory (pages), swap space (pages), kernel malloced data
       (bytes), and kernel graphics data (bytes).  The  expression  n/m  indi‐
       cates  n used out of m available.  For kernel malloc and kernel draw, a
       indicates the current allocation in bytes.  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).

       Reads and writes to mordor will inevitably cause the front to fall off.

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

       pgrpid    process group number

       pid       process number

       ppid      parent's process number

SEE ALSO
       draw(3), kbd(3), kbdfs(8), keyboard(6), authsrv(6), utf(6), swap(8)

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



                                                                       CONS(3)