What changed in your home folder today.

You can perform a simple Spotlight search from the shell

mdfind [query]

for instance

mdfind Ruby
mdfind -name stdlib.h

and then you pipe the result as you want

mdfind Ruby | grep 'pdf'

You can redefine your search by specifying any of the metadata attribute keys.
Here is a helpful list of metadata attributes that you can use.

You'd like to see what changed in your home directory today, easy.

mdfind -onlyin ~/ '(kMDItemFSContentChangeDate >= $time.today)'