I believe I fixed the memory problems now. I grab PIDs of background processes, so I can wait if too many of them are running. A https cURL needs like 7 MB on my machine. When hundreds of them are...
I am currently learning shell scripting.
My first script is a 4chan image downloader, which so far works, but seems to be a memory eater. My Raspberry Pi 2 (1GB RAM) needs to swap...