This works for all three line ending styles which Vim recognizes: DOS (Windows), Unix, and traditional Mac. The script relies on Vim's recognition of a missing line ending, saved in the 'eol' option value. Even though 'eol' is set properly, it only has any effects when 'binary' is also set. So, the core of the script simply sets 'binary' temporarily. Unfortunately, when 'binary' is set, the file is always written with Unix-format line endings. So the rest of the script manually adds the correct line endings for the current format, and removes them again after writing. augroup automatic_noeol