Convince grep to output all lines, not just those with matches

Say I have the following file: $ cat test test line 1 test line 2 line without the search word another line without it test line 3 with two test words test line 4 By default, grep returns each line that contains the search term: $ grep test test test line 1 test line 2 test line 3 with two test words test line 4 Passing the --color parameter to grep will make it highlight the portion of the line that matches the search expression, but it still only returns lines that contain the expression. Is there a way to get grep to output every line in the source file, but highlight the matches? My current terrible hack to accomplish this (at least on files that don't have 10000+ consecutive lines with no matches) is: $ grep -B 9999 -A 9999 test test  If grep can't accomplish this, is there another command-line tool that offers the same functionality? I've fiddled with [ack](https://beyondgrep.com/) , but it doesn't seem to have an option for it either.