http://blog.chinaunix.net/uid-23577393-id-1751983.html

To count how often any pattern occurs in the current buffer use the substitute
command and add the ‘n‘ flag to avoid the substitution.  The reported number
of substitutions is the number of items.  Examples: >

        :%s/./&/gn              characters     
        :%s/\i\+/&/gn           words          
        :%s/^//n                lines          
        :%s/the/&/gn            "the" anywhere
        :%s/\<the\>/&/gn        "the" as a word

You might want to reset ‘hlsearch‘ or do ":nohlsearch".
Add the ‘e‘ flag if you don‘t want an error when there are no matches.

An alternative is using |v_g_CTRL-G| in Visual mode.

If you want to find matches in multiple files use |:vimgrep|.


：%s/mystring//gn 



                                                        *count-bytes*
If you want to count bytes, you can use this:

        Visually select the characters (block is also possible)
        Use "y" to yank the characters
        Use the strlen() function: >
                :echo strlen(@")
A line break is counted for one byte.

%s            在整个文件中替换 (:help :s )
\w           匹配一个字 (word) (:help /\w )
g           替换行内所有出现的匹配 (:help :s_flags)
n           只报告匹配的数目，并不真正进行替换(:help :s_flags)


vim 显示当前正在编辑的文件名
：f
或者ctrl+g


删除匹配的行
: g/template/d