PROC(4) PROC(4)
Name
proc - Processor boxes.
Synopsis
/b/proc
/b/proc/me
/b/proc/*/name
/b/proc/*/args
/b/proc/*/stat
/b/proc/*/regs
/b/proc/*/usr
/b/proc/*/prog
/b/proc/*/events
/b/proc/*/del
/b/proc/*/legacy
/b/proc/*/vm
/b/proc/*/ns
/b/proc/*/ioN
Description
The /b/proc box supplies processing services for the system.
Each process has a box under /b/proc on a Plan B machine.
Boxes under /b/proc have names that determine the process
name. To avoid name collissions, the shell creates boxes
named /b/proc/program.N where N is a random number.
The special name /b/proc/me maps to the box for the process
that evaluates the namebeware of this when using the shell.
To access the shell's own box from the command line use the
shell variable $me.
New processes can be created by using make(2) and existing
ones can be killed by using delete(2).
Each process box has inner boxes representing process
resources. Although kernel processes have their boxes listed
in /b/proc, they don't have all the inner boxes that are
customary for user processes.
name is the box containing the name of the process box.
This is useful to obtain the real box name for so
that a process could obtain a name that is portable
to others.
args is the box containing the arguments of the process;
i.e. its command-line.
stat contains a string with the process status. Newly
created processes are said to be born, while
ready/running processes are said to be alive. Other
states are dead, for faulting processes, paused, for
stopped processes, and debugged, for traced
PROC(4) PROC(4)
processes.
regs contains the set of register values for the process.
The format is a set two-digit string (hexa) with the
size of the machine word followed by a two-digit
string (hexa) with the number of registers and by
either 8 or 16 digit strings (hexa) with the regis-
ter values.
usr contains a string with the name of the user respon-
sible for the process. The name is the same used
under /b/usr for the same human.
Besides the ones listed above, user processes also have
these inner boxes:
prog is used to contain the program executed by the pro-
cess. A newly created process starts in born state
and does not run until a binary box is either linked
or copied to its prog box. Only programs within the
same node can be linked.
events is used to post events related to the process as
well as to control event handling. A process can
write to its own event box the strings die to die
after any event post, catch to cause event posts to
raise an error instead, and ignore to cause event
posts to be ignored. Events are posted by copying a
string representing the event to the event box. Any
process can post events provided it has permission
to copy them and the system itself may post events.
Special system events starting with die: can not be
catched or ignored, and cause inmediate process
death. To arrange for a timeout event to be sent in
the future (after n milliseconds), a process can
copy a tmout n event to its event box. A periodic
timer can be set in the same way by posting a tick n
event.
del is a box that contains names for boxes that the sys-
tem should delete(2) if the process dies. When a box
is created with the Pdeldie permission bit set, the
system writes its name to the del box of the pro-
cess. The user can copy more names into it (one at a
time).
legacy is the process legacy. A process is expected to
write an error string (null is no error) to its
legacy box. By default, legacy is the same of
/b/sys/null and the process legacy is ignored. While
the process is born, legacy can be linked to a more
appropriate place.
vm is the outter box for the process virtual memory
boxes. Virtual memory boxes are described in vm(4).
A copy(2) from another vm box can be used to clone
an address space. A link(2) from another vm box can
be used to share the address space. Only address
space boxes within the same node can be linked. Both
operations are allowed only while the process is
PROC(4) PROC(4)
born.
ns contains a textual representation of the process
name space. Each import is described on a separate
line. The box exists not just for informative pur-
poses, a copy(2) from another ns box can be used to
clone a name space; A link(2) from another ns box
can be used to share the name space. Only name space
boxes within the same node can be linked. Both oper-
ations are allowed only while the process is born.
ioN boxes (where N is conventionally a number) represent
the set of stardard I/O boxes used by the process.
Number 0 is used for input, number 1 for output, and
number 2 for errors. These boxes are linked to
appropriate places according to the usr(4).
Announces
/b/proc as /proc.
Source
/src/b/port/procbox.c and /src/b/*/proc.c.
See also
spawn(3).
Bugs
Inne box regs is not implemented. It is not expected to be
implemented before starting the native port of the system.
Some special events are expected to appear after adding
debugging facilities to Plan B.
If a box is noted to be removed when the process dies, and
an error forbids the removal during process deletetion, the
box may survive the process.
The conventions for I/O boxes are undergoing severe changes.