RE: How to search all open buffers?

[Drew Adams]

Wrt searching multiple buffers, in some cases only those visiting files, in
other cases including those not visiting files:

In Icicles, you can use C-c ' (`icicle-occur') to do either. A numeric
prefix arg tells C-c ' to search multiple buffers, not just the current one.
If the arg is 99, then only buffers visiting files are candidates: C-99 C-c
'.

Your minibuffer input filters the candidates when choosing the buffers to
search. You can type a regexp that matches a particular file suffix, to
limit the candidates to file buffers in a given mode.

You can use C-! to select all buffers that match your input, or you can
choose individual buffers that match.

If you often want to search the same set of buffers or files (e.g. for a
project), then you can define the set once, save it, and reuse it later. You
can save it persistently or not.

After you have chosen the buffers to search, you type a pattern (regexp)
that you want to search for. You can change the pattern on the fly - the
search hits are updated incrementally as you type.

C-c ` (`icicle-search') is more general than C-c '. Using it you can search
multiple buffers, multiple files, or multiple regions in different buffers.
You can save such sets of regions for later reuse.

With C-c `, you first parse the target buffers, files, or regions into
search segments using a preliminary regexp, instead of just searching within
all lines as for `occur'. You then search within the segments by typing a
pattern (regexp) to match dynamically (just as for C-c ').