Setting Vim whitespace preferences by filetype

there are many ways, but here's a simple, easy to understand way. add these lines to your ~/.vimrc:

autocmd FileType html setlocal ts=2 sts=2 sw=2
autocmd FileType ruby setlocal ts=2 sts=2 sw=2
autocmd FileType javascript setlocal ts=4 sts=4 sw=4

Peter's answer is straightforward enough, but unfortunately the options aren't right. You need to use the following options instead:

autocmd Filetype html setlocal ts=2 sw=2 expandtab
autocmd Filetype ruby setlocal ts=2 sw=2 expandtab
autocmd Filetype javascript setlocal ts=4 sw=4 sts=0 noexpandtab

Also note:

• You can make vim show tab characters by using :set list.
• Once you have the tab/space options set correctly, you can make vim repair the file (replace spaces with tabs or vice versa) using the :retab! command.

+1 to Peter's answer, but Vim provides another solution as well. If you want to do something more complicated than a single setlocal, like setting up a whole bunch of options, commands, and mappings at once, then vim's filetype plugin feature comes to the rescue.

You need to have filetype plugin on or filetype plugin indent on in your .vimrc, and then to create a plugin for e.g. ruby you can create ~/.vim/ftplugin/ruby.vim. Technically you can use any commands you like in here, to be run when a Ruby file is loaded, but the recommended ones include setlocal, map <buffer>, command -buffer, and defining functions. Lots more information is in the User Guide; if you're pretty familiar with scripting vim then jump to :help 41.11, otherwise read :help usr_40 and :help usr_41.

There's also a nice vim script: DetectIndent which tries to detect the indentation of a file that you open. It's very handy if you work with many files with different coding style.

I use an autocommand in my .vimrc:

:autocmd BufReadPost * :DetectIndent