-proc -[0-9]+-status

The /proc/[PID]/status file in Linux provides detailed information about a process, where [PID] is the process ID of a running process. It contains various fields that describe the status of the process, such as memory usage, state, and other statistics.

Here's a breakdown of the contents and some of the common fields you will find in the /proc/[PID]/status file:

Common Fields in /proc/[PID]/status

1. Name

   • The name of the process.

   • Example: Name: bash

2. Pid

   • The Process ID (PID) of the process.

   • Example: Pid: 1234

3. PPid

   • The Parent Process ID (PPID), which is the PID of the process that started this process.

   • Example: PPid: 5678

4. Uid

   • User ID (UID) of the process owner.

   • Example: Uid: 1000 1000 1000 1000

5. Gid

   • Group ID (GID) of the process.

   • Example: Gid: 1000 1000 1000 1000

6. VmSize

   • The total virtual memory size of the process in kilobytes.

   • Example: VmSize: 10240 kB

7. VmRSS

   • The resident set size (RSS), which is the non-swapped physical memory the process uses, in kilobytes.

   • Example: VmRSS: 2048 kB

8. State

   • The state of the process. This can be one of the following:

     • R: Running

     • S: Sleeping

     • D: Waiting for I/O

     • Z: Zombie

     • T: Stopped

     • W: Paging

   • Example: State: S (sleeping)

9. Tgid

   • Thread Group ID. For multithreaded processes, this is the PID of the first thread.

   • Example: Tgid: 1234

10. Threads

    • The number of threads currently being used by the process.

    • Example: Threads: 2

11. TracerPid

    • The PID of the process tracing this one (if any).

    • Example: TracerPid: 0

12. FDSize

    • The number of file descriptors the process has opened.

    • Example: FDSize: 64

13. SigQ

    • The number of pending signals for the process.

    • Example: SigQ: 0/123

14. CapInh

    • Inherited capabilities for the process.

    • Example: CapInh: 00000000

15. CapPrm

    • Effective capabilities for the process.

    • Example: CapPrm: 00000000

16. CapEff

    • The process’s current capabilities.

    • Example: CapEff: 00000000

17. Seccomp

    • The process's seccomp filter mode.

    • Example: Seccomp: 0

18. Cpus_allowed

    • A bitmask of CPUs on which the process can run.

    • Example: Cpus_allowed: 00000001

19. Cpus_allowed_list

    • A more readable format of CPUs allowed.

    • Example: Cpus_allowed_list: 0

20. Mems_allowed

    • A bitmask of memory nodes that the process can use.

    • Example: Mems_allowed: 00000001

Example of /proc/[PID]/status

Name:   bash
Pid:    1234
PPid:   5678
Uid:    1000    1000    1000    1000
Gid:    1000    1000    1000    1000
State:  S (sleeping)
VmSize: 10240 kB
VmRSS:  2048 kB
Threads:        2
FDSize: 64
SigQ:   0/123
CapInh: 00000000
CapPrm: 00000000
CapEff: 00000000
Seccomp:        0
Cpus_allowed:   00000001
Cpus_allowed_list:       0
Mems_allowed:   00000001

Usage

You can use a regular expression like -proc -[0-9]+-status to find and parse the status files for processes, where:

• /proc/[PID]/status contains the status information of the process with ID PID.

• The [0-9]+ part of the regular expression will match any process ID, so it can be used to find all status files in the /proc directory.

For example, to view the status of a process with PID 1234:

cat /proc/1234/status

This gives a comprehensive snapshot of the process, useful for monitoring system performance, debugging, or gaining insight into process behavior.