NOTE FOR USERS THAT WANT TO TRY THIS OUT!

The current code on the master branch doesn’t work as documented, as a newer more powerful interface is being developed. For the doucmented interface, you want to build the latest stable tag:

$ git clone <clone url>
$ cd mmv
$ git checkout tags/v1.0.0 -b v1.0.0-master
$ cargo build -r
$ make install

mmv — multi move

mmv is a command-line utility to move multiple files in a more convenient manner than for-loops. The best way to explain this is with an example. Say you had the following files in the current directory:

$ ls
'The Fellowship of the Ring.mp4'  'The Two Towers.mp4'
'The Return of the King.mp4'

You may be excited because you’re about to watch Lord of the Rings, but the filenames have spaces in them which for various reasons is not a very good idea. You’re hacker though, so you execute the following code in your shell:

$ for old in *; do
>         new=`echo "$old" | tr ' ' '-'`
>         mv "$old" "$new"
> done

Cool, that worked. It is quite a lot to write directly into your shell though, and if the shell you’re using has a CLI that isn’t great with multi-line input you may find yourself with a negative experience.

But wait! Now you decided that actually you would like your filenames to all be in lowercase too, because it’s more consistent with the rest of your filesystem. Well cool, now you can use your shells history to navigate to the previous loop, navigate to the call to tr, and edit its parameters to 'A-Z' 'a-z'. But again, if you have a shell that doesn’t take too kindly to this longer form of script editing then you won’t have a great time (and trust me, very few shells offer a nice experience in this regard).

Let’s try to accomplish this same task using mmv:

$ mmv *

After running the above command, an instance of your editor specified by the $EDITOR variable gets launched with a list of all your files. It looks like so:

The Fellowship of the Ring.mp4
The Return of the King.mp4
The Two Towers.mp4

Now like mentioned previously, you are a hacker. This means that you use vim (or if you’re a real hacker, emacs). You’re not that cool though, so you use vim. Well thankfully vim makes renaming these files very easy:

VGu        " Go into visual-line mode, select the whole document, and lowercase
           " everything
:%s/ /-/g  " Swap all spaces for hyphens
ZZ         " Save and quit

…and just like that, we have turned all those pesky spaces into hyphens and lowercased our filenames, and all it took was 15 keypresses (that includes the enter key, and saving the file)!

Safety

Another advantage of mmv is that it’s a lot safer than your typical for-loop, or embarassingly enough even most file renaming tools I find online (lol). What do I mean by “safer”? Well consider that we want to make the following very simple file renamings:

foo → bar
bar → foo

Most tools I’ve come across for renaming files will rename foo to bar, and then oops!, the original bar file no longer exists and we just lost our data! Even if you were to do this manually (imagine a lot more files) you would need to go and move everything to a temporary directory, and move them back, and it’s kind of just a pain to do manually. Luckily mmv handles this for you!