Hello,
I've heard about the possibility to use pd without the gui.
I don't know anything about it and informations are not easy to find.
I create this topic for those who have experiences, patchs and documentation to share it.

hello.
i use -nogui if I use the pd~ subprocess. i think it makes also sense if you run a patch on an arduino or something like that,
it is a little more efficient depending on the gui.
also the ofelia standalone application runs pd without gui.
and everything that uses libpd runs pure data without gui.

I am using -nogui on a rpi 1 without X11 running, there's also the -batch flag (run off-line as a batch process). Also can be useful for a patch that listen to input. Exactly what @Jona said, I have a setup where a micro-controller is sending packet to pd to start and stop patches. The main process running at startup use the -nogui flag.