While most comic book readers these days support the cbr format, there are a few that don't. In addition, the cbr format isn't as free (as in speech) as one might like. This is a handy utility to convert cbr files to cbz, keeping the contents intact. Standard zip compression is used, so the output size may exceed the original input.
You'll need to have an 'unrar' implementation installed and accessible. On OS X with brew this is as simple as brew install unrar. On most Linuxes, you'll want to install unrar proper (sometimes called unrar-notfree), but please avoid unrar-free.
To run from source, you'll need rarfile.
To build from source, you'll need cx_Freeze.
Basic Usage is as simple as
cbr2cbz ~/comics/some-comic.cbr
which will drop some-comic.cbz in your current directory. Optionally you can specify an output directory by:
cbr2cbz ~/comics/some-comic.cbr ~/my_converted_comics/
The program will gladly handle a directory of comics too, if you'd like:
cbr2cbz ~/comics
though by default it'll only convert files actually ending in .cbr.
Building is done via cx_Freeze, just run:
python setup.py cx_Freeze
A platform compatible executable should appear in the build directory.