I noticed today that greps recursive function is different to finds recursion.
find ./ -name *.txt grep -R 'text' *.text
The above find command will search from the sub-directory down while grep will only search the current folder. The FILE_PATTERN must also match the hierarchy in grep.
To apply a file type filter in grep you can do:
grep -R --include=*.txt 'text' ./
This looks at all file from the current directory (./) but will only grep files which match the include.
An older article on Basic grep usage.