PROC(3) PROC(3)
NAME
proc - running processes
SYNOPSIS
bind #p /proc
/proc/n/ctl
/proc/n/mem
/proc/n/note
/proc/n/notepg
/proc/n/proc
/proc/n/segment
/proc/n/status
/proc/n/text
...
DESCRIPTION
The proc device serves a two-level directory structure. The
first level contains numbered directories corresponding to
pids of live processes; each such directory contains a set
of files representing the corresponding process.
The mem file contains the current memory image of the pro-
cess. A read or write at offset o, which must be a valid
virtual address, accesses bytes from address o up to the end
of the memory segment containing o. Kernel virtual memory,
including the kernel stack for the process and saved user
registers (whose addresses are machine-dependent), can be
accessed through mem. Writes are permitted only while the
process is in the Stopped state and only to user addresses
or registers.
The read-only proc file contains the kernel per-process
structure. Its main use is to recover the kernel stack and
program counter for kernel debugging.
The read-only status file contains a string with eight
fields, each followed by a space. The fields are: the pro-
cess name and user name, each 27 characters left justified;
the process state, 11 characters left justified; the six
11-character numbers also held in the process's #c/cputime
file, and the amount of memory used by the process, except
its stack, in units of 1024 bytes.
The text file is a pseudonym for the file from which the
process was executed; its main use is to recover the symbol
table of the process.
Textual messages written to the ctl file control the execu-
tion of the process. Some presume that the process is in a
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PROC(3) PROC(3)
particular state and return an error if it is not.
stop Suspend execution of the process, putting it in
the Stopped state.
start Resume execution of a Stopped process.
waitstop Do not affect the process directly but, like all
other messages ending with stop, block the process
writing the ctl file until the target process is
in the Stopped state or exits. Also like other
stop control messages, if the target process would
receive a note while the message is pending, it is
instead stopped and the debugging process is
resumed.
startstop Allow a Stopped process to resume, and then do a
waitstop action.
hang Set a bit in the process so that, when it com-
pletes an exec(2) system call, it will enter the
Stopped state before returning to user mode. This
bit is inherited across a fork(2).
kill Kill the process with extreme prejudice.
Strings written to the note file will be posted as a note to
the process (see notify(2)). The note should be less than
`ERRLEN-1' characters long; the last character is reserved
for a terminating NUL character. A read of at least
`ERRLEN' characters will retrieve the oldest note posted to
the process and prevent its delivery to the process. The
notepg file is similar, but the note will be delivered to
all the processes in the target process's note group (see
fork(2)). The notepg file is write-only.
FILES
/sys/src/9/*/mem.h
/sys/src/9/*/dat.h
SEE ALSO
cons(3)
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