linux bash, camel case string to separate by dash

I propose to use sed to do that:

NEW=$(echo MyDirectoryFileLine        \
     | sed 's/\(.\)\([A-Z]\)/\1-\2/g' \
     | tr '[:upper:]' '[:lower:]')

UPD I forget to convert to lower case, updated code

You can use s/\([A-Z]\)/-\L\1/g to find an upper case letter and replace it with a dash and it's lower case. However, this gives you a dash at the beginning of the line, so you need another sed expression to handle that.

This should work:

sed --expression 's/\([A-Z]\)/-\L\1/g' \
    --expression 's/^-//'              \
    <<< "MyDirectoryFileLine"