Bulk renaming files from TitleCase -> Title Case (space separation)

Question

I have a 38GB folder with 800 MP4 videos in it. After re-downloading it, the file name has no spacing, and all words are joined, but it's still TitleCase.

So from TitleCase I need Title Case.

What would be the most effective way of bulk renaming these files?

I remember a rename or autorename being included a long time ago in my distro, but I don't seem to have it now.

Answer 1

If you want to add spaces between each 'Words' of mp4 filename TitleCase (PascalCase to Word Separated By Spaces):

rename -n 's/\B[[:upper:]]/ $&/g' ./*.mp4

Output

rename(./FooBarBaz.mp4, ./Foo Bar Baz.mp4)

Check this post that details in depth the Perl's rename

What about rename different versions and usage ? What is the recommended way to use the Perl version especially?

Answer 2

I don't know what would be the most efficient way (I think you meant efficient), but I would quickly write a for loop like:

for file in *.mp4; do
  newname="$(echo "$file" | sed 's/\(.\)\([A-Z]\)/\1 \2/g')"
  mv "${file}" "${newname}"
done

Explanation:

  newname="$(echo "$file" | sed 's/\(.\)\([A-Z]\)/\1 \2/g')"
#        ^-------------------- Assign to  variable "newname" value…
#         ^------------------- "$()": as output by commannd in parentheses;
#                              use "" to avoid word splitting

where

echo $file | sed 's/\(.\)\([A-Z]\)/\1 \2/g'
#    ^-------------------------------------- output old file name
#          ^-------------------------------- pipe to `sed` command

sed is the name of the "stream editor"; it takes input, executes a command on it, and produces output. Here, the command is s, as in "search and replace".

s/\(.\)\([A-Z]\)/\1 \2/g
^^ ^  ^ ^      ^ ^  ^  ^
|| |^ | | ^^^  | |  |  |
\------------------------ s: search and replace
 \----------------------- /: Set the search;replace;flags separator to "/"
   || | | \|/  | \  /  |
   \--+------------------ \(…\): a "capture group" (the first one);
    |   |  |   |  ||   |         whatever is matches the content will be
    |   |  |   |  \|   |         available as \1
    \-------------------- .: We match ".", which means *any* character
        |  |   |   |   |  (which precludes this from matching at start of line)
        \------+--------- \(…\): Second capture group, \2
           \------------- [A-Z]: Match any capital letter
                   |   |
                   \----- Replacement: "\1 \2" replace
                       |  "characterbeforecapitalletter""Capitalletter" with
                       |  "characterbeforecapitalletter" "Capitalletter"
                       |
                       \- g: Flag that means "global": Repeat this until
                             end of line

Answer 3

To separate out words in title-case, like for FooBarBaz.mp4 to become Foo Bar Baz.mp4, you can do insert a space before every uppercase letter except when it's the first character in the file name, which with zsh's zmv you could do (recursively) with:

$ autoload -Uz zmv
$ zmv -n '(**/)(?)(*.mp4)' '$1$2${3//(#m)[[:upper:]]/ $MATCH}'
mv -- FooBarBaz.mp4 'Foo Bar Baz.mp4'
mv -- OnceUponATime.mp4 'Once Upon A Time.mp4'

(remove the -n for dry-run if happy).

Beware it changes Foo-Bar.mp4 to Foo- Bar.mp4.

zmv -n '(**/)(*.mp4)' '$1${2//(#b)([[:alpha:]])([[:upper:]])/$match[1] $match[2]}'

Would only insert spaces between a letter and an uppercase letter, but would not work for OnceUponATime above as the space would be inserted between n and A, but not between A and T as the A would have already be consumed by the previous substitution.

As zsh globs don't have the equivalent of perl's look around operators, working around that is more difficult. A simple approach in this case though is to just repeat the substitution an extra time:

$ zmv -n '(**/)(*.mp4)' '$1${${2//(#b)([[:alpha:]])([[:upper:]])/$match[1] $match[2]}//(#b)([[:alpha:]])([[:upper:]])/$match[1] $match[2]}'
mv -- ABCDEF.mp4 'A B C D E F.mp4'
mv -- AChristmasCarol.mp4 'A Christmas Carol.mp4'
mv -- FooBarBaz.mp4 'Foo Bar Baz.mp4'
mv -- LeSongeD\'UneNuitD\'Été.mp4 'Le Songe D'\''Une Nuit D'\'Été.mp4
mv -- LifeOfΠ.mp4 'Life Of Π.mp4'
mv -- OnceUponATime.mp4 'Once Upon A Time.mp4'

Answer 4

Other answers have described tools that allow the change based on regexes and that is a fine approach. However, those answers do not address an important point (IMHO): preview capability before actually making changes on disk (that may be hard to reverse).

Enter Emacs and its dired mode, in particular wdired, documented in the manual. One would open dired for the directory containing the files, toggle wdired to make the file names editable, make changes - most likely using interactive regex search and replace, review the changes, and finally commit them to disk.

I am aware that installing Emacs for this one use case is a heavy-handed approach, but I would point out that it handles file names with difficult characters, e.g. spaces, trivially.