Changing a file's line endings in Emacs

There are several different conventions for representing the end of a line in a text file:

• Unix systems use a single line feed character (LF, 0x0A);
• Microsoft Windows (and before that, MS-DOS) uses a carrage return followed by a line feed (CR-LF, 0x0D 0x0A); and
• The original Macintosh used a single carriage return character (CR, Ox0D).

Thankfully, a LF-CR pair has never been used!

Converting line endings using emacs

It is possible to change the end-of-line convention using emacs, with the set-buffer-file-coding-system function (which is normally mapped to C-x RET f). When it prompts you for the new coding system, enter either “unix”, “dos” or “mac”.

Converting line endings using Unix commands

This is easier than trying to remember cryptic commands like:

tr -d '\r'
sed 's/$/^M/'

And having to worry about getting them to work because of different variations in sed and shell environments (e.g. when using bash the ^M is typed using Ctrl-v Ctrl-m).

If your system has the unix2dos and dos2unix commands installed (e.g. Cygwin and most Linux distributions do) use them. Otherwise, emacs lives up to its reputation as the kitchen sink tool.