procfs(5)

NAME

procfs - process file system

SYNOPSIS

proc            /proc   procfs  rw 0 0

DESCRIPTION

The process file system, or procfs, implements a view of the

system process table inside the file system. It is normally mounted

on /proc, and
is required for the complete operation of programs such as

ps(1) and
w(1).

The procfs provides a two-level view of process space, un

like the previous FreeBSD 1.1 procfs implementation. At the highest lev

el, processes
themselves are named, according to their process ids in dec

imal, with no
leading zeros. There is also a special node called curproc

which always
refers to the process making the lookup request.

Each node is a directory which contains the following en

tries:

Each directory contains several files:

ctl a write-only file which supports a variety of con

trol operations.

Control commands are written as strings to the ctl

file. The
control commands are:
attach stops the target process and arranges for

the sending

process to become the debug control process.

detach continue execution of the target process and

remove it

from control by the debug process (which

need not be the
sending process).

run continue running the target process until a

signal is

delivered, a breakpoint is hit, or the tar

get process
exits.

step single step the target process, with no sig

nal delivery.
wait wait for the target process to come to a

steady state

ready for debugging. The target process

must be in this
state before any of the other commands are

allowed.

The string can also be the name of a signal, lower

case and without the SIG prefix, in which case that signal is de

livered to the
process (see sigaction(2)).

The procctl(8) utility can be used to clear trace

points in a
stuck process.

dbregs The debug registers as defined by struct dbregs in

dbregs is cur

rently only implemented on the i386 architecture.

etype The type of the executable referenced by the file

entry.

file A symbolic link to the file from which the process

text was read.

This can be used to gain access to the process' sym

bol table, or
to start another copy of the process. If the file

cannot be
found, the link target is `unknown'.

fpregs The floating point registers as defined by struct

fpregs in

fpregs is only implemented on machines which have

distinct general purpose and floating point register sets.

map A map of the process' virtual memory.

mem The complete virtual memory image of the process.

Only those

address which exist in the process can be accessed.

Reads and
writes to this file modify the process. Writes to

the text segment remain private to the process.

note Used for sending signals to the process. Not imple

mented.

notepg Used for sending signal to the process group. Not

implemented.

regs Allows read and write access to the process' regis

ter set. This

file contains a binary data structure struct regs

defined in regs
can only be written when the process is stopped.

rlimit This is a read-only file containing the process cur

rent and maxi

mum limits. Each line is of the format rlimit

current max, with
-1 indicating infinity.

status The process status. This file is read-only and re

turns a single

line containing multiple space-separated fields as

follows:

+o command name
+o process id
+o parent process id
+o process group id
+o session id
+o major,minor of the controlling terminal, or

-1,-1 if there is

no controlling terminal.

+o a list of process flags: ctty if there is a con

trolling ter

minal, sldr if the process is a session leader,

noflags if
neither of the other two flags are set.

+o the process start time in seconds and microsec

onds, comma

separated.

+o the user time in seconds and microseconds, comma

separated.
+o the system time in seconds and microseconds,

comma separated.
+o the wait channel message
+o the process credentials consisting of the effec

tive user id

and the list of groups (whose first member is

the effective
group id) all comma separated.

+o the hostname of the jail in which the process

runs, or `-' to

indicate that the process is not running within

a jail.

In a normal debugging environment, where the target is

fork/exec'd by the
debugger, the debugger should fork and the child should stop

itself (with
a self-inflicted SIGSTOP for example). The parent should

issue a wait
and then an attach command via the appropriate ctl file.

The child process will receive a SIGTRAP immediately after the call to

exec (see
execve(2)).

Each node is owned by the process's user, and belongs to

that user's primary group, except for the mem node, which belongs to the

kmem group.

FILES

/proc normal mount point for the procfs.
/proc/pid directory containing process informa

tion for pro

cess pid.

/proc/curproc directory containing process informa

tion for the

current process

/proc/curproc/cmdline the process executable name
/proc/curproc/ctl used to send control messages to the

process
/proc/curproc/etype executable type
/proc/curproc/file executable image
/proc/curproc/fpregs the process floating point register

set
/proc/curproc/map virtual memory map of the process
/proc/curproc/mem the complete virtual address space of

the process
/proc/curproc/note used for signaling the process
/proc/curproc/notepg used for signaling the process group
/proc/curproc/regs the process register set
/proc/curproc/rlimit the process current and maximum rlim

it
/proc/curproc/status the process' current status

SEE ALSO

mount(2), sigaction(2), unmount(2), mount_procfs(8), proc

ctl(8),
pseudofs(9)

AUTHORS

This manual page written by Garrett Wollman, based on the

description
provided by Jan-Simon Pendry, and revamped later by Mike

Pritchard.

BSD September 3, 2004

BSD