Question

When using grep, it will highlight any text in a line with a match to your regular expression.

What if I want this behaviour, but have grep print out all lines as well? I came up empty after a quick look through the grep man page.

Answer 1

Use ack. Check out its --passthru option here: ack. It has the added benefit of allowing full Perl regular expressions.

    $ ack --passthru 'pattern1' file_name

    $ command_here | ack --passthru 'pattern1'

You can also do it using grep like this:

    $ grep --color -E '^|pattern1|pattern2' file_name

    $ command_here | grep --color -E '^|pattern1|pattern2'

This will match all lines and highlight the patterns. The ^ matches every start of the line but won’t get printed/highlighted since it’s not a character.

(Note that most of the setups will use –color by default. You may not need that flag).