multi-occur
multi-occur is an interactive compiled Lisp function in `replace.el
'.
(multi-occur BUFS REGEXP &optional NLINES)
Show all lines in buffers BUFS containing a match for REGEXP.
This function acts on multiple buffers; otherwise, it is exactly like
`occur'. When you invoke this command interactively, you must specify
the buffer names that you want, one by one.
See also `multi-occur-in-matching-buffers'.