PROCFS(4) FreeBSD Kernel Interfaces Manual PROCFS(4)
NAME
procfs - process file system
SYNOPSIS
proc /proc procfs rw 0 0
DESCRIPTION
This functionality is deprecated. Users are advised to use
libprocstat(3) and kvm(3) instead.
The process file system, or procfs, implements a view of the system
process table inside the file system. It is normally mounted on /proc.
The procfs provides a two-level view of process space, unlike the
previous FreeBSD 1.1 procfs implementation. 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
curproc which always refers to the process making the lookup request.
Each node is a directory which contains the following entries:
dbregs The debug registers as defined by struct dbregs in
<machine/reg.h>. dbregs is currently 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' symbol 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
<machine/reg.h>. fpregs is only implemented on machines which
have distinct general purpose and floating point register sets.
map A collection of lines describing the memory regions of the
process, where each line contains the following fields:
start-address The starting address for the region
(inclusive).
end-address The ending address for the region (exclusive).
resident The number of resident pages.
private-resident The number of resident pages that were private
to the process.
obj The virtual address of the struct vm_object
kernel data structure describing the memory
region.
access A three character string comprising the
characters `r', `w' and `x', denoting read,
write, and execute permissions respectively.
The lack of a permission is represented by `-'.
ref_count The number of references to the region.
shadow_count The number of VM objects that this region is a
shadow for.
flags The flags for the object, see the flags named
OBJ_* in <vm/vm_object.h>.
copy-on-write Whether the region is copy-on-write. One of:
COW A copy-on-write region.
NCOW A non-copy-on-write region.
needs-copy Whether the region needs a copy. One of:
NC The region needs a copy.
NNC The region does not need a copy.
type The type of the region. One of:
dead A region associated with a dead VM
object.
device A region backed by device memory.
none A region not backed by anything.
phys A region backed by physical memory.
swap A region backed by swap.
unknown A region of unknown type.
vnode A region backed by a file.
fullpath The path to the file backing the memory region,
or `-' if there is no such file.
cred One of:
CH The region is being charged to the user
specified in the `charged-uid' field.
NCH The region is not being charged to any
user.
charged-uid The UID of the user being charged, or -1 if no
user is being charged.
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 implemented.
notepg Used for sending signal to the process group. Not implemented.
osrel Allows read and write of the kernel osrel value assigned to the
process. It affects the compatibility shims that are turned on
and off depending on the value. Initial process value is read
from the ABI note tag in the executed ELF image, and is zero if
the tag not supported by binary format or was not found.
regs Allows read and write access to the process' register set. This
file contains a binary data structure struct regs defined in
<machine/reg.h>. regs can only be written when the process is
stopped.
rlimit This is a read-only file containing the process current and
maximum limits. Each line is of the format rlimit current max,
with -1 indicating infinity.
status The process status. This file is read-only and returns 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 device name of the controlling terminal, or a minus sign
("-") if there is no controlling terminal.
o a list of process flags: ctty if there is a controlling
terminal, 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 microseconds, 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 effective UID
o the process real UID
o group list, starting with the effective GID, 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.
Each node is owned by the process's user, and belongs to that user's
primary group.
FILES
/proc normal mount point for the procfs.
/proc/pid directory containing process information for
process pid.
/proc/curproc directory containing process information for the
current process
/proc/self directory containing process information for the
current process
/proc/curproc/cmdline the process executable name
/proc/curproc/etype executable type
/proc/curproc/exe executable image
/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/osrel the process osrel value
/proc/curproc/regs the process register set
/proc/curproc/rlimit the process current and maximum rlimit
/proc/curproc/status the process' current status
EXAMPLES
To mount a procfs file system on /proc:
mount -t procfs proc /proc
SEE ALSO
procstat(1), mount(2), sigaction(2), unmount(2), kvm(3), libprocstat(3),
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.
FreeBSD 15.1-STABLE-HBSD June 23, 2024 PROCFS(4)