emacs 使用

undo command
C-/
C-x u
C-_
       
C-t      Transpose two characters (transpose-chars).
M-t      Transpose two words (transpose-words).
C-M-t    Transpose two balanced expressions (transpose-sexps).
C-x C-t  Transpose two lines (transpose-lines).

M-- M-l     Convert last word to lower case. Note Meta-- is Meta-minus.
M-- M-u     Convert last word to all upper case.
M-- M-c     Convert last word to lower case with capital initial.

M-$   Check and correct spelling of the active region or the word at point (ispell-word).
M-x ispell  Check and correct spelling in the active region or the entire buffer.
M-x ispell-buffer  Check and correct spelling in the buffer.