How do I manipulate character case in search and replace in vim?

Question

for example, I have:

  double foo = 0.0;  
  double bar = 0.0;

and I want to write some sort of search to find each variable and change it to:

  double Foo = 0.0;  
  double Bar = 0.0;

I dont want to do these one variable at a time (e.g. :%s/foo/Foo/g) but rather all at once, something close to

:%s/  double \(\w\+\)/  double \1/c 

(and somehow capitialize the first character of \1)

Answer 1

Use the \u prefix for the match in the replace clause:

For one at a time:

:%s/ double \(\w\+\)/ double \u\1/c

For all at once:

:%s/ double \(\w\+\)/ double \u\1/g

If you want to make the whole match uppercase use the \U and \E delimiters:

:%s/ double \(\w\+\)/ double \U\1\E/g

Answer 2

Use \u

%s/ double \(\w\+\)/ double \u\1/c