The result is a Number, which is the window-ID of the first window associated with buffer {buf}. For the use of {buf}, see bufname() above. If buffer {buf} doesn't exist or there is no such window, -1 is returned. Example:

echo "A window containing buffer 1 is " .. (bufwinid(1))

Only deals with the current tab page. See win_findbuf() for finding more.

Can also be used as a method:

FindBuffer()->bufwinid()