Rename file and encapsulte last X number of charactors, before the extension, in square brackets

Question

I've been using youtube-dl to download an entire youtuber's channel for archival purposes. I had been using the default naming pattern for naming the videos which uses the video's title, then a hyphen, the 11 character video id and finally, the file's extension.

e.g.

title of the video - (an example)-oHg5SJYRHA0.mp4

For future downloads, I've removed the hyphen and placed the video id within square brackets. The problem is that I've already got hundreds of videos following the old naming scheme that I don't want to waste bandwidth on re-downloading just to get the new naming scheme.

How can I rename files of varying length so that a "]" is placed before the ".mp4" and they hyphen, 11 spaces/characters before the "].mp4" is replaced with a "["?

e.g.

title of the video - (an example)[oHg5SJYRHA0].mp4

[EDIT] I forgot to specify that I'd prefer a solution that'll work on Linux and/or FreeNAS/BSD.

Answer 1

Under Linux, you can use rename command like that:

rename 's/-\w{11}(?=\.mp4$)/[$&]/' *.mp4

Regex explanation:

-           # a hyphen
\w{11}      # 11 word characters
(?=         # positive lookahead, make sure we have after:
  \.mp4     # a dot followed by mp4
  $         # end of string
)           # end lookahead

Replacement:

[           # opening square bracket
$&          # the whole match (i.e. 11 characters)
]           # closing squarre bracket

If the 11 characters can be other than word character, use the following:

rename 's/-\K.{11}(?=\.mp4$)/[$&]/' *.mp4

Where . matches any character but newline.

Answer 2

If you don't mind to use a 3rd party tool, which I would recommend for one time use, I would recommend advancedrenamer, it's portable and free.

Otherwise you can use powershell, this description tells you everything you need to know. Let us know if you get stuck.