Emacs Word Commands in C and Java Modes

The Problem

You use the Emacs commands:

Command	Action
M-f	Move forward by one word
M-b	Move backward by one word
M-d	Delete word ahead of the cursor
M-DEL	Delete word behind cursor
M-t	Transpose words
M-@	Mark word
M-u	Upcase word
M-l	Downcase word
M-c	Capitalize word

They work beautifully with ordinary text but not so great in C or Java modes. For example, the arrows in the image below show where the cursor will skip to if you use M-f to skip forward starting at the first arrow.

The problem here is that C-mode doesn't recognize "_" as part of a "word".

The Solution

There is an easy fix for this: simply add the following lines to your .emacs file:

01 (add-hook 'c-mode-common-hook
02        (lambda ()
03          (modify-syntax-entry ?_ "w" c-mode-syntax-table)))
04 (add-hook 'java-mode-hook
05        (lambda ()
06          (modify-syntax-entry ?_ "w" java-mode-syntax-table)))

The image below shows where the cursor will skip to after the hook is installed.

All word-related commands will recognize "_" as part of a "word" in C and Java modes.

Problem solved.