shell command knowledge base

I'm not an expert on linux/android shell commands, but know enough to realize how useful this feature can be. I think it would be nice to have a section here perhaps with a tutorial and repository of useful items and methods. I've seen numerous questions I think could be handled with sh().

$if(sh("cat filename")~="Q","#ff0000","#00ff00")$

$sh("am")$

am start -n