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Proc - Status file

To get the status information of a process, all you have to do is read the file /proc/PID/status:

cat /proc/self/status

returns:

Name:   cat
State:  R (running)
Tgid:   5452
Pid:    5452
PPid:   743
TracerPid:      0						(2.4)
Uid:    501     501     501     501
Gid:    100     100     100     100
FDSize: 256
Groups: 100 14 16
VmPeak:     5004 kB
VmSize:     5004 kB
VmLck:         0 kB
VmHWM:       476 kB
VmRSS:       476 kB
VmData:      156 kB
VmStk:        88 kB
VmExe:        68 kB
VmLib:      1412 kB
VmPTE:        20 kb
VmSwap:        0 kB
Threads:        1
SigQ:   0/28578
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
CapInh: 00000000fffffeff
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
voluntary_ctxt_switches:        0
nonvoluntary_ctxt_switches:     1

This shows you nearly the same information you would get if you viewed it with the ps command. In fact, ps uses the proc file system to obtain its information. But you get a more detailed view of the process by reading the file /proc/PID/status.

Contents of the status files (as of 2.6.30-rc7)

Field	Content
Name	Filename of the executable.
State	State (R is running, S is sleeping, D is sleeping in an uninterruptible wait, Z is zombie, T is traced or stopped).
Tgid	Thread group ID.
Pid	Process id.
PPid	Process id of the parent process.
TracerPid	PID of process tracing this process (0 if not).
Uid	Real, effective, saved set, and file system UIDs.
Gid	Real, effective, saved set, and file system GIDs.
FDSize	Number of file descriptor slots currently allocated.
Groups	Supplementary group list.
VmPeak	Peak virtual memory size.
VmSize	Total program size.
VmLck	Locked memory size.
VmHWM	Peak resident set size (“high water mark”).
VmRSS	Size of memory portions.
VmData	Size of data, stack, and text segments.
VmStk	Size of data, stack, and text segments.
VmExe	Size of text segment.
VmLib	Size of shared library code.
VmPTE	Size of page table entries.
VmSwap	Size of swap usage (the number of referred swapents).
Threads	Number of threads.
SigQ	Number of signals queued/max. number for queue.
SigPnd	Bitmap of pending signals for the thread.
ShdPnd	Bitmap of shared pending signals for the process.
SigBlk	Bitmap of blocked signals.
SigIgn	Bitmap of ignored signals.
SigCgt	Bitmap of catched signals.
CapInh	Bitmap of inheritable capabilities.
CapPrm	Bitmap of permitted capabilities.
CapEff	Bitmap of effective capabilities.
CapBnd	Bitmap of capabilities bounding set.
Cpus_allowed	Mask of CPUs on which this process may run.
Cpus_allowed_list	Same as previous, but in “list format”.
Mems_allowed	Mask of memory nodes allowed to this process.
Mems_allowed_list	Same as previous, but in “list format”.
voluntary_ctxt_switches	Number of voluntary context switches.
nonvoluntary_ctxt_switches	Number of non voluntary context switches.