[EmanueleAina]

I mean, I know that it sets a variable, I can't even guess what are the effect of setting that variable.

And "look at the source" is a sad answer, no matter if the source is a shell script or C program.

The point is that with your example you need domain knowledge, knowing bash is not enough: what does the pexp assignment do, what rc_reload=NO means, should flags be specified in the daemon variable or that's meant to only contain the binary, does that path be full or it takes in consideration a standard PATH?

And now you got two things to know: the bash (or even strictly posix sh) language (which, admittedly, isn't the best one in the world) and the domain specific functions/variables.

This isn't much different than with systemd: the language is much more simple and far less surprising being INI-like (the same as .desktop files), and it's basically just setting a list of rather well documented variables.