vimL, how to get alternate window's current buffer number

Question

Say, with 2 windows open in vim, cursor is window 2, how can I get the current buffer of the alternate window (window 1 in this case)?

Answer 1

Try this:

" current window buffer number
:echo winbufnr(winnr())

" 'previous' window buffer number
:echo winbufnr(winnr('#'))

" Name of the 'previous' window buffer number
:echo bufname(winbufnr(winnr('#')))

"Previous" here means the window you have switched from to the current with, for example, <C-w>w. So if you have 3+ windows opened then the last command will show you buffer name of the window you were in "previously" :)

To make it more "generic" you can try to play with winnr() function and friends.