What feature of the spark-shell enhances user interaction with Spark?

The feature that enhances user interaction with Spark is the interactive command-line interface offered by the spark-shell. This interface allows users to enter commands and see immediate results, making it highly suitable for exploratory data analysis, quick prototyping, and testing small code snippets. Users can run individual Spark commands and immediately evaluate their output without the need to submit entire scripts, which fosters an interactive development experience. This immediacy contributes to faster iteration and experimentation when working with large datasets.

While batch processing capabilities are important for handling large volumes of data efficiently, they focus more on the execution model rather than user interactivity. Automatic library updates can help keep environments current but do not directly impact how users engage with Spark. Similarly, remote server connections expand access to Spark clusters but do not pertain specifically to enhancing the interactivity provided by the spark-shell.