During installation, you would get the error below if you have the old RgGen (version < 0.9).

ERROR:  Error installing rggen:
        "rggen" from rggen-core conflicts with installed executable from rggen

To resolve this confliction, there are three solutions.

1. Uninstall the old RgGen

Hit the command below to uninstall the old RgGen before installing the latest RgGen.

$ gem uninstall rggen

2. Override rggen executable with the latest one forcibly

Add --force option to the installation command.

$ gem install --force rggen
$ gem install --force rggen-core

3. Change the directory where the latest rggen executable is installed

Add --bindir option to the installation command and add the directory to PATH environment variable.

$ gem install --bindir path/to/rggen/bin rggen
$ gem install --bindir path/to/rggen/bin rggen-core
$ export PATH="path/to/rggen/bin:$PATH"

If you chose either solution 1 or 2 then the you cannot use the old RgGen. Therefore, you have to chose solution 3 if you also need to use the old RgGen.