How to do max-depth search in ack and grep?

You can couple find with the -exec argument. example:

find . -maxdepth 1 -exec grep foo {} \;

This can be scaled, i.e. -maxdepth 2

Use -n for no-recurse:

$ ack -n foo

grep is not recursive by default, and you should use the -r flag only if you want a recursive search.

You can search the current directory with grep as follows:

$ grep -- foo *