Search for string and get count in vi editor

THE way is

:%s/pattern//gn

You need the n flag. To count words use:

:%s/\i\+/&/gn   

and a particular word:

:%s/the/&/gn        

See count-items documentation section.

If you simply type in:

%s/pattern/pattern/g

then the status line will give you the number of matches in vi as well.

:%s/string/string/g will give the answer.

(similar as Gustavo said, but additionally: )

For any previously search, you can do simply:

:%s///gn

A pattern is not needed, because it is already in the search-register (@/).

"%" - do s/ in the whole file
"g" - search global (with multiple hits in one line)
"n" - prevents any replacement of s/ -- nothing is deleted! nothing must be undone!
(see: :help s_flag for more informations)

(This way, it works perfectly with "Search for visually selected text", as described in vim-wikia tip171)

:g/xxxx/d

This will delete all the lines with pattern, and report how many deleted. Undo to get them back after.