The process file system, or
implements a view of the system process table inside the file system.
It is normally mounted on
and is required for the complete operation of programs such as
provides a two-level view of process space, unlike the previous
At the highest level, processes themselves are named, according to
their process ids in decimal, with no leading zeros.
There is also a
special node called
which always refers to the process making the lookup request.
Each node is a directory which contains the following entries:
Each directory contains several files:
a write-only file which supports a variety
of control operations.
Control commands are written as strings to the
The control commands are:
stops the target process and arranges for the sending
process to become the debug control process.
continue execution of the target process and
remove it from control by the debug process (which
need not be the sending process).
continue running the target process until
a signal is delivered, a breakpoint is hit, or the
target process exits.
single step the target process, with no signal delivery.
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
in which case that signal is delivered to the process
utility can be used to clear tracepoints in a stuck process.
The debug registers as defined by
In machine/reg.h .
is currently only implemented on the i386 architecture.
The type of the executable referenced by the
A symbolic link to the file from which the process text was read.
This can be used to gain access to the process' symbol table,
or to start another copy of the process.
If the file cannot be found, the link target is
The floating point registers as defined by
In machine/reg.h .
is only implemented on machines which have distinct general
purpose and floating point register sets.
A map of the process' virtual memory.
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.
Used for sending signals to the process.
Used for sending signal to the process group.
Allows read and write access to the process' register set.
This file contains a binary data structure
In machine/reg.h .
can only be written when the process is stopped.
This is a read-only file containing the process current and maximum
Each line is of the format
rlimit current max
The process status.
This file is read-only and returns a single line containing
multiple space-separated fields as follows:
parent process id
process group id
major , minor
of the controlling terminal, or
if there is no controlling terminal.
a list of process flags:
if there is a controlling terminal,
if the process is a session leader,
if neither of the other two flags are set.
the process start time in seconds and microseconds,
the user time in seconds and microseconds,
the system time in seconds and microseconds,
the wait channel message
the process credentials consisting of
the effective user id
and the list of groups (whose first member
is the effective group id)
all comma separated.
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
The parent should issue a
and then an
command via the appropriate
The child process will receive a
immediately after the call to exec (see
Each node is owned by the process's user, and belongs to that user's
primary group, except for the
node, which belongs to the
normal mount point for the
directory containing process information for process
directory containing process information for the current process