Q:

How do I remove all but the last 12 characters from filenames of different lengths using Mac terminal?

How do I remove the last 12 characters from these files, and change it from this:
RE0001_cdea_3000_001_000_0000.MP4
175c_3000_000_000_0000.MP4
To this:
001_000_0000.MP4
000_000_0000.MP4
I'm guessing is the inverse of something like for f in *; do mv "$f" "${f:12}"; done.  But that removed the first 12 characters, and since the file length will change, I'm hoping the start at the file type and count the left. Thanks for your help!

A:

Using a negative offset counts from the end.
mv "$f" "${f: -12}"

Note that when using a negative offset you have to put a space before the offset. Otherwise it's interpreted as ${f:-defaultvalue}
But it seems like you forgot to count the .MP4 suffix, you want the last 16 characters.
mv "$f" "${f: -16}"

