Compare two directories contents on your Mac using diff

If you want to see the difference between two folders on a Mac, launch the Terminal and read on. Using the command line tool ‘diff’ you can easily compare the contents of any two directories, here’s the command we’ll use to achieve this:

diff -rq directory1 directory2 >> differences.txt

This executes the diff command comparing directory1 and directory2 (if you have a folder with a space in the file name, just put it in quotes like so: “folder one”), and then redirects the output of that command to a file named differences.txt. Here’s an example and how the actual printout will look:
diff -rq "old music" "new music" >> musicfolders.txt
Now look in the present working directory for the file you just created via outputting the diff command, in this case the file is musicfolders.txt and the contents can be viewed in any text editor, command line or otherwise. Opening the text file you’ll see something like this:
Only in old music: song1.mp3
Only in old music: song2.mp3
Only in old music: song3.mp3
Only in new music: instrumental1.mp3
Only in new music: instrumental1.mp3

If you want to view the file from the command line, try:
more musicfolders.txt
Otherwise just navigate to the containing directory and open it in your favorite text editor. If you’d prefer not to create a text file with the changes, just leave off the output redirection of the command. You might want to pipe the output to something like ‘more’ to make it easier to scan though:
diff -rq "old music" "new music" | more

It’s worth mentioning that this command will work in Mac OS X as well as most Unix based OS’s.