How can you automatically remove trailing whitespace in vim

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.

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 :-)

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

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