How can I set different textwidths for specific file extensions in .vimrc?

Question

I would like to have a default textwidth of 80 characters except for a few file extensions like txt. The following lines appear to work, except for the first time when I edit (and create) a txt file.

setlocal textwidth=80
autocmd bufreadpre *.txt set textwidth=0

What is the correct way to do this?

Answer 1

First, you've got the scopes the wrong way; use :set for the global default and :setlocal for the buffer-local override in the :autocmd.

Second, BufReadPre is only for reading existing files, not new ones; that's why it doesn't work the first time. Instead, you should use BufNew,BufRead; this captures both cases, and only applies after the file was read, so it will still work when you use modelines or have a setting in an filetype plugin.

Third, the :autocmd solution tends to become unwieldy once you have many customizations. If you only want to enable a setting for certain filetypes, put the corresponding :setlocal commands into ~/.vim/after/ftplugin/<filetype>.vim, where <filetype> is the actual filetype (e.g. java). (This requires that you have :filetype plugin on; use of the after directory allows you to override any default filetype settings done by $VIMRUNTIME/ftplugin/<filetype>.vim.)

Answer 2

use setlocal

autocmd bufreadpre *.txt setlocal textwidth=0

instead of set.

With setlocal you make sure that the value you're setting is set in the current buffer, not for all buffers.