Colorized grep — viewing the entire file with highlighted matches

Question

I find grep\'s --color=always flag to be tremendously useful. However, grep only prints lines with matches (unless you ask for context lines). Give

Answer 1

It might seem like a dirty hack.

grep "^\|highlight1\|highlight2\|highlight3" filename

Which means - match the beginning of the line(^) or highlight1 or highlight2 or highlight3. As a result, you will get highlighted all highlight* pattern matches, even in the same line.