What I'm trying to do is to compare the content of two different files. I don't know what I'm doing wrong, but things I searched online regarding diff command didn't work.

For example if fileA content is this:

```
AAA:111
BBB:222
CCC:333

```

And fileB content is:

```
AAA:111
BBB:222

```

All I want to see as an output is the difference which is CCC:333. No "<" no ">", just plainly CCC:333. I want to use this later in the bash script I'm working on.

Also would it matter if those files were reversed? I mean if it was fileB containing CCC:333?

I don't know if it matters, but the files I'm working on are MAC addresses.

Is the diff command I was trying to use case sensitive?