`winwidth(0)` returns the width of the current window.  However, if vim has multiple vertical splits, forming multiple windows, `winwidth(0)` would only return the width of the current window.

For example, let say the terminal has 80 columns across.  Without, any vertical splits, `echo winwidth(0)` would return 80.  If `<C-W>v` is used however, `echo winwidth(0)` would return a smaller number, less than 80, equal to the width of one of the split windows.

How can I get the full terminal width without forcing the cursor to jump through all vertical splits (for example, with `windcmd l`)?