How to remove trailing whitespace in Vim

You've raised two prices on Byte Burrito's menu and added chorizo, and the commit won't go in. git diff --check says menu.js:2: trailing whitespace., and the same about lines 4 and 5, but all three look fine. The trouble is after the last comma, a space or two on two lines and a tab on the third, and nothing at the end of a line shows on screen.

The fix reads left to right. :%s substitutes on every line in the file, and the pattern between the first two slashes is \s\+$. \s is a space or a tab, \+ means one or more of them, and $ holds them to the end of the line. Nothing goes between the next two slashes, so whatever matched is replaced with nothing.

The e flag only matters when there's nothing to delete. Without it, :%s/\s\+$// on a file that's already clean ends with E486: Pattern not found: \s\+$. Typed by hand, that's only noise. In a mapping, the error also stops the keys that come after it.

It matters most when the command runs by itself. With autocmd BufWritePre * %s/\s\+$//e in your vimrc, Vim strips every file just before it writes it. Leave out the e and every save of a clean file shows the error. The hook also leaves the cursor on the last line it changed.

Search for the pattern on its own, /\s\+$ and ↵, and every run of spaces or tabs at a line end lights up. n takes the cursor to the next one. Neovim keeps them lit until you type :nohlsearch. In Vim, type :set hlsearch first, or the highlight goes when you press ↵.

To look at every line end at once, type :set list. Vim then puts a $ where each line really ends, so trailing spaces show up as a gap before it, and each tab shows as ^I. Neovim shows each trailing space as - and a tab as >. :set nolist puts the screen back. If you'd rather have them marked all the time while you work, :match ErrorMsg /\s\+$/ paints every trailing run in the error colour, and :match none takes it off.

\s takes tabs as well as spaces. To strip only spaces, put a plain space in its place: :%s/ \+$//e. Tabs at the start of lines are a different job, which :retab does (see how to set the tab size).

In an old file, stripping everything makes your commit touch lines you never meant to change, and whoever reviews it has to read past them. git diff --check only complains about lines you added, so fixing those is enough.

The search puts the cursor on the first space of a match. From there D, which deletes from the cursor to the end of the line, takes exactly the trailing run. n goes on to the next match, and . repeats the delete. To skip a match that isn't yours, press n again.

A file that came from Windows can show ^M at the end of some of its lines. That's a carriage return, the first half of a Windows line ending. \s doesn't match it, so :%s/\s\+$//e leaves it where it is, and the spaces in front of it too. Take the carriage returns out first with :%s/\r//g, then strip the spaces.

When every line ends the Windows way, Vim reads the file as a DOS file and shows no ^M at all, and :%s/\r//g finds nothing. :set ff? answers fileformat=dos. Type :set ff=unix, save with :w, and the file is written back with plain line endings.