Switching case of characters

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Tip 49 Printable Monobook Previous Next

created 2001 · complexity basic · version 5.7


You can change the case of text:

Toggle case "HellO" to "hELLo" with g~ then a movement.
Uppercase "HellO" to "HELLO" with gU then a movement.
Lowercase "HellO" to "hello" with gu then a movement.

Alternatively, you can visually select text then press ~ to toggle case, or U to convert to uppercase, or u to convert to lowercase.

[edit] Examples

~
Toggle case of the character under the cursor, or all visually-selected characters.
3~
Toggle case of the next three characters.
g~3w
Toggle case of the next three words.
g~iw
Toggle case of the current word (inner word – cursor anywhere in word).
g~$
Toggle case of all characters to end of line.
g~~
Toggle case of the current line (same as V~).

The above uses ~ to toggle case. In each example, you can replace ~ with u to convert to lowercase, or with U to convert to uppercase. For example:

U
Uppercase the visually-selected text.
First press v or V then move to select text.
If you don't select text, pressing U will undo all changes to the current line.
gUU
Change the current line to uppercase (same as VU).
gUiw
Change current word to uppercase.
u
Lowercase the visually-selected text.
If you don't select text, pressing u will undo the last change.
guu
Change the current line to lowercase (same as Vu).

[edit] Title case

The :s substitute command can change case (see :help s/\u).

The following converts the current line to Title Case (all lowercase, except for initial uppercase letters):

:s/\<\(\w\)\(\w*\)\>/\u\1\L\2/g

Explanation The search pattern is \<\(\w\)\(\w*\)\> which searches for \< (beginning of word), then \w (a word character), then \w* (zero or more word characters), then \> (end of word). The \(...\) create subexpressions to be recalled with \1 and \2 in the replacement. The replacement is \u\1\L\2 which substitutes the two subexpressions transformed: The \u converts the first character of what follows to uppercase, while \L converts all of what follows to lowercase.

[edit] Twiddle case

With the following (for example, in vimrc), you can visually select text then press ~ to convert the text to UPPER CASE, then to lower case, then to Title Case. Keep pressing ~ until you get the case you want.

function! TwiddleCase(str)
  if a:str ==# toupper(a:str)
    let result = tolower(a:str)
  elseif a:str ==# tolower(a:str)
    let result = substitute(a:str,'\(\<\w\+\>\)', '\u\1', 'g')
  else
    let result = toupper(a:str)
  endif
  return result
endfunction
vnoremap ~ y:call setreg('', TwiddleCase(@"), getregtype(''))<CR>gv""Pgv

[edit] References

[edit] Comments

The following will skip single-letter words and words that aren't in uppercase. It also accounts for non-english latin characters.

:s/\v\C<([A-ZÀ-Ý])([A-ZÀ-Ý]+)>/\u\1\L\2/g

--Jenny 165.2.186.10 19:05, April 5, 2012 (UTC)

Nice, thanks. I added \C to your command above to make the search case sensitive (it won't skip lowercase words if 'ignorecase' is set, unless \C is present). JohnBeckett 09:58, April 6, 2012 (UTC)
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