This is an english translation of http://www.guideitech.com/apple/come-rinominare-facilmente-un-gruppo-di-file-su-os-x-yosemite/ While I translated it mostly to practice my Italian, it's a great article and shows a cool feature on Yosemite if you don't want to deal with doing this at the command line :) Also please let me know if you find any mistakes or bad translations!
I’m sure there are hundreds of unorganized files on your macs right this moment. Vacation photos, PDF documents, downloads, TV series, or whatever. The first step in organizing these contents is to give them proper names.
Renaming a group of files can be frustrating, particularly in the case of hundreds or thousands of photos. Until now it was necessary to use a 3rd-party tool to rename a group of files at the same time, but now this functionality has been integrated into OS X Yosemite. Let’s take a look at how it works.
First off, open Finder and go to the folder where the files you want to rename are located. Select them all and and right-click on them. Among the various options, select Rename X elements.
In my example I used a folder with notes taken during university lectures I attend. It would be nice to rename all files with names like “Lesson 1”, “Lesson 2”, etc. Three options are presented in the popup that will open: Replace text, Add text, and Format. Let’s see what these functions do.
This option is really simple. Write the text to replace in the search: field, and the new text to insert in the Substitute with: field and the substitution is made automatically.
This option allows the adding of text at the beginning or end of the file name.
This is the most powerful and most interesting option, since it allows for the removal of the actual file name and the replacement of it with one created ad-hoc. Let me explain. There are a couple of options that can be configured. Let’s start with Format name: and Located in:. At the beginning of the article I said that I want to rename my notes to Lesson 1, Lesson 2, etc. To automate the process, in Format name: I’ll chose Name and index because I want the numbers to be automatically added at the end of the name. It’s also possible to select, between the other options, Name and counter and Name and date.
In Customize format we are going to write the text that needs to be repeated in the file names that we want to rename. In my case I inserted the text Lesson (adding one space at the end of the name so as to separate the text from the numbers that will be automatically inserted). In the Located in: field we can decide where to insert the numbers, either at the end or at the beginning of the file name. In my case I chose after the name. Finally, in the Start numbering from: field we must put the number for which we want the numbering of the files to start at. In my case I put 1.
When we press the Remove button, all my files will at that time be automatically formatted as Lesson 1, Lesson 2, etc.
Using this function is very easy. If something isn’t clear and you have any questions to ask, you can do so via the comments.