unix - textwidth - vim truncate long lines

VIM textwidth has no effect (4)

This feels like a dumb question, but I can't find an answer on the Internet (or in VIM help). I'm using VIM 7.2 on Mac OS X. All I want to do is wrap my lines at 72 characters, but doing

:set textwidth=72 

has no effect. The textwidth is being set correctly (I can see that when I just query ":set textwidth"), but neither existing lines nor new lines that I type after setting textwidth get wrapped. If I start a new line, still doesn't wrap. Open and close the file, no change. I've also tried :set wrapmargin=72 (with textwidth=0), with no effect.

What am I missing here?

I had this exact same issue and found the following solved the issue well enough for me:

autocmd FileType python setlocal textwidth=79 formatoptions+=t

Feel free to change python to be your file type of choice (e.g. * or comma separated list python,ruby,go,sh,javascript)

See :h fo-table for details of formatoptions

I was looking for an answer to the same question and had to scramble around a bit before I found the solution in the VIM docs. So, i thought i will update the thread and save others the time.

The problem in my case was that the default ftplugin was disabling textwidth.

Just updating your .vimrc with (:set tw=79 && :set formatoptions+=t) won't work since the fplugins are sourced after vimrc.

Here are the steps that i followed:

1) find out what your current formatoptions (inside vim)

:set formatoptions?
formatoptions=croql (note no 't')

2) create a filetype.vim file as suggested by vimdocs (http://vimdoc.sourceforge.net/htmldoc/filetype.html#ftplugin-overrule)

Overrule the settings after loading the global plugin.
You must create a new filetype plugin in a directory from the end of
'runtimepath'.  For Unix, for example, you could use this file:
    vim ~/.vim/after/ftplugin/fortran.vim
In this file you can change just those settings that you want to change.

3) add the line :set formatoptions+=t && :set textwidth=79 in that file.

Voila! next time when you open the file it will set the textwidth to your desired characters.

As a debugging aid you can always check which file is overriding your vimrc setting by prepending your command with verbose. So for e.g. if i want to check who updated the formatoptions last, i would type

:verbose set formatoptions? 
Last set from ~/.vim/after/ftplugin/fortan.vim

Vim won't do anything unless requested. textwidth will have an effect for currently edited lines if you either have t (for non-comments only), c (for comments only) or both in formatoptions (if a is not present there, then it will autowrap only when you reach the margin set by textwidth), or if you use gq to reformat your text. If I am not mistaking, you can set such formatexpr or formatprg so that textwidth will be ignored.

What does

:set formatexpr?
:set indentexpr?
:set cindent?
:set filetype?
:set paste?


At least one of those (and I think all of them) will override the setting for textwidth.

For example, if you're editing a C source file, the C indent rules override textwidth.