Question: I'm trying to use sed to clean up lines of URLs to extract just the domain.

So from:

```
http://www.suepearson.co.uk/product/174/71/3816/

```

I want:

```
http://www.suepearson.co.uk/

```

(either with or without the trailing slash, it doesn't matter)

I have tried:

```
 sed 's|\(http:\/\/.*?\/\).*|\1|'

```

and (escaping the non-greedy quantifier)

```
sed 's|\(http:\/\/.*\?\/\).*|\1|'

```

but I can not seem to get the non-greedy quantifier (`?`) to work, so it always ends up matching the whole string.

Answer: 
Neither basic nor extended Posix/GNU regex recognizes the non-greedy quantifier; you need a later regex. Fortunately, Perl regex for this context is pretty easy to get:

```
perl -pe 's|(http://.*?/).*|\1|'

```
sed -E interprets regular expressions as extended (modern) regular expressions

Update: -E on MacOS X, -r in GNU sed.