Rename to Start Case or Initial Caps in Bash

Question

I need a oneliner to rename all files in a directory from

SomeThing.TXT
NOT A FILE.ogg
sensitive lalala.doc

to

Something.txt
Not A File.ogg
Sensitive Lalala.doc

In other words: first letters of words are capital case and everything else is lowercase. This is called Start case or initial caps. It is very close to "Title case". The file extension should be lower case.

Most existing questions seem to only deal with UPPERCASE.MKV or lowercase.mkv filenames, none seem to cover Capitalized Case.mkv (example).

All the common tools like pipes, sed, perl, grep and more can be used.

Answer 1

If you have access to perl rename, (installed by default as rename on Debian-based systems, available as perl-rename on many others), you could run:

rename  's/.*/lc($&)/e; s/(^| )./uc($&)/ge' *

Explanation:

The rename program will run a perl expression on each of its input file names. Here, the first substitution operation (s///) will replace everything (.*) with itself ($& is whatever was matched) but lower cased (lc($&)). The second, will match every character that's after a space or at the beginning of the file name ((^| )) and replace it with its upper cased version (uc($&)).

Run with the -n flag to test without making any changes:

$ rename -n 's/.*/lc($&)/e; s/ ./uc($&)/ge' *
rename NOT A FILE.ogg not A File.ogg
rename sensitive lalala.doc sensitive Lalala.doc
rename SomeThing.TXT something.txt

---

You could also use a shell loop and perl:

for f in *; do 
    mv "$f" "$(perl -lpe 's/.*/lc($&)/e; s/(^| )./uc($&)/ge' <<<"$f")"
done

This is the same command as in the rename above, only we feed it each file in the directory and use command substitution to rename.

You could easily modify this to avoid overwriting existing files:

for f in *; do 
    target="$(perl -lpe 's/.*/lc($&)/e; s/(^| )./uc($&)/ge' <<<"$f")"; 
    [ -e "$target" ] && 
        echo "File \"$target\" exists, skipping \"$f\"" || 
        mv "$f" "$target"; 
done

Answer 2

"De-capitalizing" answered here:

for i in *
do
  mv "$i" "$( echo $i | tr '[:upper:]' '[:lower:]')"
done

Capitalizing already answered here:

for i in *
do
  mv "$i" "$( echo $i | sed 's/[ ]*/\u&/g')"
done

Answer 3

This works on Bash 3.2.57 for Mac OSX

Preview (doesn't change anything):

IFS=$'\n';FOLDER=new;for F in $(ls -1);do EXT="${F##*.}";NAME="${F%.*}";NEW=$(echo "$NAME"| perl -pe 's/[ _-]([A-z0-9])([^ _-]+)/ \U\1\L\2/g');echo "cp '$F' '$FOLDER/$NEW.$EXT'";done

If the preview looks good, you can use this to rename and cp into subfolder:

IFS=$'\n';FOLDER=new;[ -d $FOLDER ] || mkdir $FOLDER;for F in $(ls -1);do EXT="${F##*.}";NAME="${F%.*}";NEW=$(echo "$NAME"| perl -pe 's/[ _-]([A-z0-9])([^ _-]+)/ \U\1\L\2/g');cp -v "$F" "$FOLDER/$NEW.$EXT";done

Notes:

• Will not change the file extension.
• Should handle numbers correctly.
• If you have other chars you want to be converted to spaces, just add them to the character class: [ _-]
• Avoids conflicting names by making a copy of each file into a subfolder. This gives you an "undo" option. Another way to handle this would be to rename all files, while adding a prefix like _My New File Name.jpg, then rename all of those to versions without the _.

Answer 4

I came up with a quick solution in one-liner form:

for f in *; do mv -i "$f" "`echo $f | sed -e 's/\(.*\)/\L\1/' -e 's/\( .\)/\U\1/g' -e 's/\(^.\)/\U\1/g'`"; done

Or in readable (but marginally less comfortable to copy paste form):

for f in *; do 
    mv -i "$f" "`echo $f | 
     sed -e 's/\(.*\)/\L\1/' -e 's/\( .\)/\U\1/g' -e 's/\(^.\)/\U\1/g'`"; 
done

This command uses sed to mv each file to a file with the same name but in which all characters are first turned to lowercase, then each combination of space followed by any character is turned to uppercase, then the first character is turned uppercase.

This will ask before overwriting.

Remove -i if you want it automatically to overwrite.