Emacs

isearch is probably one of the most widely known Emacs commands. Every Emacs user knows that they can run it using C-s (to search forward) and C-r to search backwards. Everyone also knows they can keep pressing C-s and C-r to go over the list of matches in the current buffer. Even at this point that’s a very useful command. But that doesn’t even scratch the surface of what isearch can do!

After you’ve started isearch you can actually do a lot more than pressing C-s and C-r:

• Type DEL to cancel last input item from end of search string.
• Type RET to exit, leaving point at location found.
• Type LFD (C-j) to match end of line.
• Type M-s M-< to go to the first match, M-s M-> to go to the last match. (super handy)
• Type C-w to yank next word or character in buffer onto the end of the search string, and search for it. (very handy)
• Type C-M-d to delete character from end of search string.
• Type C-M-y to yank char from buffer onto end of search string and search for it.
• Type C-M-z to yank from point until the next instance of a specified character onto end of search string and search for it.
• Type M-s C-e to yank rest of line onto end of search string and search for it.
• Type C-y to yank the last string of killed text.
• Type M-y to replace string just yanked into search prompt with string killed before it.
• Type C-q to quote control character to search for it.
• Type C-x 8 RET to add a character to search by Unicode name, with completion.

C-g while searching or when search has failed cancels input back to what has been found successfully. C-g when search is successful aborts and moves point to starting point.

You can also toggle some settings when isearch is active:

• Type M-s c to toggle search case-sensitivity.
• Type M-s i to toggle search in invisible text.
• Type M-s r to toggle regular-expression mode.
• Type M-s w to toggle word mode.
• Type M-s _ to toggle symbol mode.
• Type M-s ' to toggle character folding.
• Type M-s SPC to toggle whitespace matching.

In incremental searches, a space or spaces normally matches any whitespace defined by the variable search-whitespace-regexp; see also the variables isearch-lax-whitespace and isearch-regexp-lax-whitespace.

Type M-s e to edit the search string in the minibuffer. That one is super useful! Also supported is a search ring of the previous 16 search strings:

• Type M-n to search for the next item in the search ring.
• Type M-p to search for the previous item in the search ring.
• Type C-M-i to complete the search string using the search ring.

Last, but not least - you can directly search for the symbol/thing at point:

• Type M-s . to search for the symbol at point. (useful in the context of programming languages)
• Type M-s M-. to search for the thing (e.g. word or symbol) at point.

One of the most useful parts of that is the fact that a region is a thing. So you can mark a region (e.g. with expand-region or mark-*) and M-s M-. to immediately search for other instances of that text. Powerful stuff!

Tip: You don’t really have to remember all those keybindings - just remember you can press C-h b to show them. (after you’ve started isearch) Most of the above text is coming straight from the docstring of isearch.

It’s funny that I’ve been using Emacs for almost 20 years, I use isearch numerous times every day and I still often forget about much of its functionality. There’s more to isearch, though. Did you know it’s widely customizable as well? If you check its options with M-x customize-group isearch you’ll see there are over 30 (!!!) options there! Admittedly, I never used any of them, but you’ve got quite a lot of opportunities to tweak the behavior of isearch if you want to. Here’s an example of a customization some of you might find useful:

;; When isearching, enable ``M-<``, ``M->``, ``C-v`` and ``M-v`` to skip between matches
;; in an intuitive fashion. Note that the ``cua-selection-mode`` bindings
;; for ``C-v`` and ``M-v`` bindings are not supported. (``setq isearch-allow-motion t isearch-motion-changes-direction t``)

I hope you learned something useful today! Keep searching (the Emacs docs)!`___`