How to get all descendent child process id of pid in c in linux [duplicate]

Answer 1

If you are looking for commands to see the process tree, check below commands.

ps -ejH
ps axjf
pstree $PID

Check the man pages of ps and pstree commands.

Answer 2

Iterating through /proc is the "standard" way to do this. That's how ps and friends (pstree, etc.) are implemented.