In Linux, everything is a file. Even processes.
Don't believe me? Open your terminal.
Exploring /proc
Go to /proc. You will see numbered directories.
cd /proc
ls
# 1 123 456 ...
These numbers are PIDs (Process IDs). Directory 1 is the init process (or systemd).
Hacking a Process
Let's say Python is running. Find its PID.
pgrep python
# 1234
Go to /proc/1234.
* cmdline: The command that started it.
* environ: The environment variables (Secrets! 🤫).
* fd: File descriptors (files it has opened).
Conclusion
If you want to know what a program is doing, don't guess. Look at /proc. It's the dashboard of the kernel.