Best approach to get all recursive child processes of a PID from either the `/proc` filesystem or equivalent kernel API?

Question

Let's say, I have chrome running, which has 100 different processeses, not all of which are direct children. What's the best way to programmatically get all of the processes from either the procfs or the any syscall may be (I believe getrusage only allows calling process), given the PID of the main chrome parent in the hierarchy?

Also, is there any API that's equivalent to PSAPI in Windows which provides OpenProcess, GetProcessMemoryInfo etc, that allows you to iterate through memory efficiently, rather than parsing the procfs?

Most efficient way please. No calling other processes like ps, pstree, pgrep, etc.

Side context: This is mostly an educational exercise to find the most efficient way to do this, which I started going down trying to write a simple script in nodejs to try and get all the processes programatically and then, calculate the sum of the memory taken by the process tree, including each.

Answer 1

I'm actually the author of a C++ library that is designed to do exactly that - pfs.

pfs attempts to make all the interesting information inside procfs accessible through a very simple API. If you find it lacking any useful information, please create an issue, and I'll try to add it.

Seeing that you require that information from Node.js, you might be able to use the library for "inspiration" or for research purposes (as in, understand where the information is located).

Regarding the process tree: The procfs contains the parent PID of every process (find it under stat and/or status). You can enumerate all the running processes and store them into a container and then iterate over it while drawing or retaining the order you require.