\< and \> in sed

Question

I'm reading this regex tutorial and it says:

The pattern to search for the word "the" would be "\<[tT]he>".

How come this doesn't output bar bar?

○ → echo "foo bar" | sed -E 's/\<foo\>/bar/'
foo bar

Can \< and \> be used in sed?

Then maybe BSD sed doesn't work this way and the tutorial is for GNU sed. — Mateusz Piotrowski, Oct 10 '17 at 20:58
Ah, that explains it. `sed` implementations differ. Try `sed 's/[[:<:]]foo[[:>:]]/bar/'` — Wiktor Stribiżew, Oct 10 '17 at 20:58
This would be pretty convenient. Does the OSX version have an alternative? — Daniel Kaplan, Oct 10 '17 at 21:00

anubhava · Answer 1 · 2017-10-10T21:05:26.477

1

\< and \> are used for word boundaries but it is platform dependent.

On OSX sed you need to use [[:<:]] and [[:>:]] for the same:

echo "foo food bar" | sed -E 's/[[:<:]]foo[[:>:]]/bar/'

bar food bar

However if you can install gnu sed on OSX using brew package installer then you can use:

echo "foo food bar" | gsed -E 's/\bfoo\b/bar/'

bar food bar

edited Oct 10 '17 at 21:05

answered Oct 10 '17 at 21:00

anubhava

https://stackoverflow.com/a/5734237/3832970 – Wiktor Stribiżew Oct 10 '17 at 21:00
1

Documentation for `[[:<:]]` and `[[:>:]]` can be found in `man re_format`, which documents the style of regular expressions accepted by `sed`. – chepner Oct 10 '17 at 21:01

1 Answers1