If you look at :h magic
:
Examples:
after: \v \m \M \V matches
'magic' 'nomagic'
$ $ $ \$ matches end-of-line
. . \. \. matches any character
* * \* \* any number of the previous atom
~ ~ \~ \~ latest substitute string
() \(\) \(\) \(\) grouping into an atom
| \| \| \| separating alternatives
\a \a \a \a alphabetic character
\\ \\ \\ \\ literal backslash
\. \. . . literal dot
\{ { { { literal '{'
a a a a literal 'a'
The default node in regular expressions is \m
(just magic), so you need to use \{
for the brace to seen as an operator:
/\{ E58 E60 E554 E870
\{n,m} Matches n to m of the preceding atom, as many as possible
\{n} Matches n of the preceding atom
\{n,} Matches at least n of the preceding atom, as many as possible
\{,m} Matches 0 to m of the preceding atom, as many as possible
Try:
%s/.\{30}/xx/