Automatically increase &columns upon :vsplit, but not beyond maximum

Question

I wanted vim to increase its &columns automatically when I do a :vsplit, so I implemented the advice found here: https://groups.google.com/forum/#!topic/vim_use/R4gg-YdPHJM

Basically, you add:

autocmd WinEnter * if winwidth(0) < 80 | set columns+=80 | wincmd = | endif

to .vimrc.

However, in terminal vim, I opened 3 windows side-by-side, and the &columns increased beyond the size of my terminal.

I tried to do this:

if &columns + 79 > $COLUMNS | set columns=$COLUMNS | else | set columns+=79 | endif

but it didn't work, saying, "Number required after =: columns=$COLUMNS".

How can I get &columns to increase but only up to a maximum of the $COLUMNS environment variable?

Answer 1

COLUMNS is a shell variable, not an environmental variable.

You could do something like this:

This exports COLUMNS before invoking vim

alias vim='export COLUMNS;vim $*'

However, the value of the exported COLUMNS variable won't be updated if you resize your terminal window while you are running vim.

Answer 2

Gets the terminal's columns directly without using an environmental variable

let cols = system('tput cols')
if &columns + 79 > cols | set columns=cols | else | set columns+=79 | endif