How can you automatically remove trailing whitespace in vim

I am getting 'trailing whitespace' errors trying to commit some files in Git.

I want to remove these trailing whitespace characters automatically right before I save Python files.

Can you configure Vim to do this? If so, how?

I found the answer here.

Adding the following to my .vimrc file did the trick:

autocmd BufWritePre *.py :%s/\s\+$//e

The e flag at the end means that the command doesn't issue an error message if the search pattern fails. See :h :s_flags for more.

Compilation of above plus saving cursor position:

function! <SID>StripTrailingWhitespaces()
  if !&binary && &filetype != 'diff'
    let l:save = winsaveview()
    keeppatterns %s/\s\+$//e
    call winrestview(l:save)
  endif
endfun

autocmd FileType c,cpp,java,php,ruby,python autocmd BufWritePre <buffer> :call <SID>StripTrailingWhitespaces()

If you want to apply this on save to any file, leave out the second autocmd and use a wildcard *:

autocmd BufWritePre,FileWritePre,FileAppendPre,FilterWritePre *
  \ :call <SID>StripTrailingWhitespaces()

I also usually have a :

match Todo /\s\+$/

in my .vimrc file, so that end of line whitespace are hilighted.

Todo being a syntax hilighting group-name that is used for hilighting keywords like TODO, FIXME or XXX. It has an annoyingly ugly yellowish background color, and I find it's the best to hilight things you don't want in your code :-)

I both highlight existing trailing whitespace and also strip trailing whitespace.

I configure my editor (vim) to show white space at the end, e.g.

with this at the bottom of my .vimrc:

highlight ExtraWhitespace ctermbg=red guibg=red
match ExtraWhitespace /\s\+$/
autocmd BufWinEnter * match ExtraWhitespace /\s\+$/
autocmd InsertEnter * match ExtraWhitespace /\s\+\%#\@<!$/
autocmd InsertLeave * match ExtraWhitespace /\s\+$/
autocmd BufWinLeave * call clearmatches()

and I 'auto-strip' it from files when saving them, in my case *.rb for ruby files, again in my ~/.vimrc

function! TrimWhiteSpace()
    %s/\s\+$//e
endfunction
autocmd BufWritePre     *.rb :call TrimWhiteSpace()

Here's a way to filter by more than one FileType.

autocmd FileType c,cpp,python,ruby,java autocmd BufWritePre <buffer> :%s/\s\+$//e

I saw this solution in a comment at VIM Wikia - Remove unwanted spaces

I really liked it. Adds a . on the unwanted white spaces.

Put this in your .vimrc

" Removes trailing spaces
function TrimWhiteSpace()
  %s/\s*$//
  ''
endfunction

set list listchars=trail:.,extends:>
autocmd FileWritePre * call TrimWhiteSpace()
autocmd FileAppendPre * call TrimWhiteSpace()
autocmd FilterWritePre * call TrimWhiteSpace()
autocmd BufWritePre * call TrimWhiteSpace()

Copied and pasted from http://blog.kamil.dworakowski.name/2009/09/unobtrusive-highlighting-of-trailing.html (the link no longer works, but the bit you need is below)

"This has the advantage of not highlighting each space you type at the end of the line, only when you open a file or leave insert mode. Very neat."

highlight ExtraWhitespace ctermbg=red guibg=red
au ColorScheme * highlight ExtraWhitespace guibg=red
au BufEnter * match ExtraWhitespace /\s\+$/
au InsertEnter * match ExtraWhitespace /\s\+\%#\@<!$/
au InsertLeave * match ExtraWhiteSpace /\s\+$/

This is how I'm doing it. I can't remember where I stole it from tbh.

autocmd BufWritePre * :call <SID>StripWhite()
fun! <SID>StripWhite()
    %s/[ \t]\+$//ge
    %s!^\( \+\)\t!\=StrRepeat("\t", 1 + strlen(submatch(1)) / 8)!ge
endfun

A solution which simply strips trailing whitespace from the file is not acceptable in all circumstances. It will work in a project which has had this policy from the start, and so there are no such whitespace that you did not just add yourself in your upcoming commit.

Suppose you wish merely not to add new instances of trailing whitespace, without affecting existing whitespace in lines that you didn't edit, in order to keep your commit free of changes which are irrelevant to your work.

In that case, with git, you can can use a script like this:

#!/bin/sh

set -e # bail on errors

git stash save commit-cleanup
git stash show -p | sed '/^\+/s/ *$//' | git apply
git stash drop

That is to say, we stash the changes, and then filter all the + lines in the diff to remove their trailing whitespace as we re-apply the change to the working directory. If this command pipe is successful, we drop the stash.

The other approaches here somehow didn't work for me in MacVim when used in the .vimrc file. So here's one that does and highlights trailing spaces:

set encoding=utf-8
set listchars=trail:·
set list

For people who want to run it for specific file types (FileTypes are not always reliable):

autocmd BufWritePre *.c,*.cpp,*.cc,*.h,*.hpp,*.py,*.m,*.mm :%s/\s\+$//e

Or with vim7:

autocmd BufWritePre *.{c,cpp,cc,h,hpp,py,m,mm} :%s/\s\+$//e

If you trim whitespace, you should only do it on files that are already clean. "When in Rome...". This is good etiquette when working on codebases where spurious changes are unwelcome.

This function detects trailing whitespace and turns on trimming only if it was already clean.

The credit for this idea goes to a gem of a comment here: https://github.com/atom/whitespace/issues/10 (longest bug ticket comment stream ever)

autocmd BufNewFile,BufRead *.test call KarlDetectWhitespace()

fun! KarlDetectWhitespace()
python << endpython
import vim
nr_unclean = 0
for line in vim.current.buffer:
    if line.rstrip() != line:
        nr_unclean += 1

print "Unclean Lines: %d" % nr_unclean
print "Name: %s" % vim.current.buffer.name
cmd = "autocmd BufWritePre <buffer> call KarlStripTrailingWhitespace()"
if nr_unclean == 0:
    print "Enabling Whitespace Trimming on Save"
    vim.command(cmd)
else:
    print "Whitespace Trimming Disabled"
endpython
endfun

fun! KarlStripTrailingWhitespace()
    let l = line(".")
    let c = col(".")
    %s/\s\+$//e
    call cursor(l, c)
endfun

autocmd BufWritePre *.py execute 'norm m`' | %s/\s\+$//e | norm g``

This will keep the cursor in the same position as it was just before saving

autocmd BufWritePre * :%s/\s\+$//<CR>:let @/=''<CR>