Grep regex lookahead or start of line (or lookbehind or end of line)
I want to match a string that can contain the character type before the match, or the match can start at the beginning of the line (same for the end of the line).
For a minimal example, consider text
that I would like to match either at the beginning of a line or at the end of a line, or between two non-word characters, or some combination. The easiest way to do this is to use word boundaries (
), but that doesn't match; similar cases happen for other desired matches with non-word characters in them.
I am currently using
, which works satisfactorily, but will also match non-word characters (like a dash) that appear immediately before and after the word, if available. I do this in grep, so when I can easily pipe the output to sed, I use the grep option
, which is disabled when I connect to another command (for obvious reasons).
, it seems to work, but also discards the color in match in the output file. While I could call the helper tools again, I would love it if it was a quick and easy solution.
EDIT: I misunderstood the operator
; it just removes all text from the match before it was used. Unsurprisingly, this did not result in output color.
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If you are using grep, you must use the option
, or lookarounds and
will throw errors. This means that you also have negative images at your disposal. Here's a simpler version of your regex:
Also, keep in mind that
are lookaheads . The wording of your title suggests that you may have gotten these confusions, a common beginner mistake.
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