Linux Rename command uppercase first letter

Question

I'm writing a Bash script for cleaning up in my music.

I wanted it to format all the file names and making them and so with a little internet search I wrote this line:

sed -i -e 's/[-_]/ /g' -e 's/ \+/ /g' -e **'s/\<[a-z]/\U&/g'** -e "s/$artist //g" -e "s/$album //g"

Which I used to add the file names to a text file and then sed it, but then I didn't know how to apply the new names to the files.

So then I started experimenting with rename and managed to get the exact same result except for the bolded parts, which is supposed to make every first letter in a word uppercase.

rename 's/[-_]/ /g' * && rename 's/\s+/ /g' * && **rename 's/\s\w{1}/*A-Z*/g' *** && rename 's/^\d+[[:punct:]]\s//g' * && rename "s/$artist\s//g" * && rename "s/$album\s//g" * && rename "s/($ext)//g" *

Now, the code in rename is working (satisfactorily at least), finding only one letter after a SPACE character, but it's the replacement that is problematic. I've tried numerous different approaches, all leaving me with the result that the first letter in focus get exchanged to exactly A-Z in this case.

In the rename manual page it says to make lower case uppercase you do 's/a-z/A-Z/g' but it's easy to figure that it only applies when it finds a-z A-Z. So this is what I need help with.

A bonus would be if someone knows how to do it like in the sed example, where the \< matches the beginning of each word, because at the moment, my rename command won't apply to the very first word and neither will it apply if there are multiple discs looking like "Disc name [Disc 1]" for obvious reasons.

Answer 1

This is sort-of a Perl question, since rename is written in Perl, and instructions for how to perform the renaming are a Perl command.

In a s/// in order for the substitution to know which letter to insert the upper-case version of, it has to ‘capture’ the letter from the input. Parentheses in the pattern do this, storing the captured letter in the variable $1. And \u in a substitution makes the next character upper-case.

So you can do:

$ rename 's/\s(\w)/ \u$1/g' *

Note that the replacement part has to insert a space before the upper-case letter, because the pattern includes a space and so both the space and the original letter are being replaced. You can avoid this by using \b, a zero-width assertion which only matches at a word boundary:

$ rename 's/\b(\w)/\u$1/g' *

Also you don't need the {1} in there, because \w (like other symbols in regexs) matches a single character by default.

Finally, the example in rename(1) is actually y/A-Z/a-z/, using the y/// operator, not s///. y/// is a completely different operator, which replaces all occurrences of one set of letters with another; that isn't of use to you here, where it's only some characters you want making upper-case.