\S matches everything that isn't whitespace.

```python
>>> import re
>>> foo = re.compile(r'^foo (\S+)$')
>>> foo.match('foo 1.2.3.4').group(1)
'1.2.3.4'
>>> foo.match('foo 2001:0000::/29').group(1)
'2001:0000::/29'
>>> foo.match('foo ::/128').group(1)
'::/128'
```