Plexus IO is a set of plexus components, which are designed for use in I/O operations. These I/O operations are doing nothing spectacular. For example, Commons IO is a much more powerful library in the same area. However, the implementation as a plexus component allows reuse in Maven.
The following component groups are currently available:
Plexus IO components are typically very simple components, who could very well live as part of the Plexus Utils. They do not, because Plexus Utils is a dependency of the Plexus Component API, which is in turn a dependency of the Plexus IO test suite (of course, a Plexus container is required to test components, even if they are POJO's). In other words, Plexus Utils cannot contain components, because that would introduce a circular dependency.