PROCFS

This is a tiny procfs file system that allows read-only access to a few attributes of a task or thread. This tiny procfs fs file system can be built into the system by enabling:

CONFIG_FS_PROCFS=y

It can then be mounted from the NSH command like like:

nsh> mount -t procfs /proc

Example:

NuttShell (NSH) NuttX-6.31
nsh> mount -t procfs /proc

nsh> ls /proc
/proc:
 0/
 1/

nsh> ls /proc/1
/proc/1:
 status
 cmdline

nsh> cat /proc/1/status
Name:       init
Type:       Task
State:      Running
Priority:   100
Scheduler:  SCHED_FIFO
SigMask:    00000000

nsh> cat /proc/1/cmdline
init

nsh> sleep 100 &
sleep [2:100]
nsh> ls /proc
ls /proc
/proc:
 0/
 1/
 2/

nsh> cat /proc/2/cmdline
<pthread> 0x527420

Process user and group

With CONFIG_SCHED_USER_IDENTITY=y, /proc/<pid>/status has two more lines. Uid: gives the real and the effective user ID of the task group of <pid>. Gid: gives the real and the effective group ID:

Uid:        1000 1000
Gid:        1000 1000

stat() of /proc/<pid> and of the files in it gives the effective user and group ID of the task group in st_uid and st_gid.