_ _ _ _ _ _ _ _ _ _ _ _ _
Actually, typing random strings in the Finder does the equivalent of filename completion. (Discussion in comp.os.linux.misc on the intuitiveness of commands: file completion vs. the Mac Finder.)
_ _ _ _ _ _ _ _ _ _ _ _ _
^__^
(xx)\_______
(__)\ )\/\
U ||----w |
|| ||
grep -i 'palavra' nome_ficheiro.txt