Power up your locate command

locate

I'm sure many people know that Emacs comes with a locate command. This command, if you're on a Linux system, will find all files on your system that match a particular pattern. The advantage of locate over find when searching the whole system, is that it is much faster, since it uses a pre-computed database. This database is updated periodically, you can force an update with:

sudo updatedb

Of course find is faster if you need to search only a specific directory instead of the whole system, but sometimes you just don't know that directory.

counsel-locate

Dynamic

The way locate works it that it asks you for a query, which is glob-based instead of regex-based, and then prints the results to a static buffer.

On the other hand, counsel-locate is dynamic: each time you input a new character a new locate query is ran, and the old one is terminated. On my system, it takes around 2 seconds for a query to complete, so it requires a bit of patience.

Regex-based

I like regex way more than globs for some reason. Here's the command called for the input mp3$:

locate -i --regex mp3$

Of course, the standard ivy-mode method is used to build the regex from a list of space separated words. So the input fleet mp3$ will result in:

locate -i --regex \\(fleet\\).*?\\(mp3$\\)

You could go your own way and update the regex matcher to be ivy--regex-fuzzy, which results in:

locate -i --regex f.*l.*e.*e.*t.* .*m.*p.*3$

But I think less matches is usually better than more matches.

Multi-exit

This is just the coolest feature. Basically, for each file you locate, you can easily:

• Open it in Emacs (default).
• Open it with xdg-open, so that PDF files are forwarded to evince and MP3 files are forwarded to rhythmbox etc.
• Open it in dired.

Here's an example of how to do it. First I call counsel-locate, which I like to bind to C-x l. Then I enter emacs pdf$ and wait around 2 seconds for the 248 results to come up. Then I scroll to the 18th result and press C-o to open up the hydra-based option panel:

The last column (Action) is newer than others. As you can see, it has 3 exit points, which I can scroll with w and s. And currently I'm on the default exit point, which would open the file in Emacs.

For the next screenshot:

• I pressed s twice to change the action to dired.
• I pressed c to make the current action execute each time a new candidate is selected.

So now, I could just scroll through all my directories on my system that contain PDF files related to Emacs by just holding j.

A similar thing can be done for music tracks:

• C-x l dire mp3$ to get the list of all Dire Straits tracks on my system.
• C-o s to switch the action from "open in Emacs" to "xdg-open".
• From here, I could open one track after another by pressing C-M-n repeatedly. Or I can press c and then j repeatedly.

I've been experimenting with opening EPS and PDF files in quick succession. It's still a work in progress, since I need to use a special wmctrl script to prevent the Emacs window from losing focus each time a new Evince instance is opened.

Outro

You can check out the new feature by installing counsel from MELPA. It will automatically fetch ivy-mode as well. When you enable ivy-mode, besides doing all your completion, it will also remap switch-to-buffer to ivy-switch-buffer. That command also has a multi-exit: pressing C-o sd instead of C-m will kill the selected buffer instead of switching to it. It's a very minor optimization: instead of C-m C-x k you press C-o sd, however you could e.g. use C-o scjjjj to kill five buffers at once.

While the idea of multi-exits is powerful, it's hard to find places to use it efficiently. I think counsel-locate is a nice place for it, although it could work without it:

• Find file in Emacs with C-m in the completion interface.
• Call dired-jump with C-x C-j.
• Type ! and xdg-open RET.
• Select and kill the unneeded file with C-x k.

I hope you see now why I prefer C-o sd.