cbr2cbz is a simple command line utility to convert your comic book archive files from CBR to CBZ. It can be useful to make uniform your comic book library, or to make sure your comic book reader can read the metadata when it does not work with CBR files (as I do with ComicBookLover for iOS with metadata filled with ComicBookLover for Mac OS X).
You must have the unrar utility. You can install it easily on Mac OS X with homebrew by using brew install unrar.
gem install cbr2cbz
cbr2cbz [options] file ...
You can specify many files to convert. If you specify a directory, it will convert every CBR file inside it.
Use the -k switch if you want to keep the CBR file.