5.0 Using the Command Line Interface (CLI)
The Apache OpenNLP Command Line Interface (CLI) is a powerful tool for users who need to perform NLP tasks, train models, or conduct evaluations without writing Java code. It provides a direct, scriptable interface to the library’s core functionalities, making it ideal for rapid prototyping, data preprocessing, and model assessment.
The general syntax for invoking a tool via the CLI follows a consistent pattern, typically involving the tool’s name, the path to the required model, and redirection for input and output files.
$ opennlp <ToolName> <path_to_model> < input.txt > output.txt
The CLI supports the same core functionalities available through the Java API. The table below summarizes the commands for several common tasks.
| Task | Tool Name | Required Model | Function |
| Tokenization | TokenizerME | en-token.bin | Breaks text into tokens. |
| Sentence Detection | SentenceDetector | en-sent.bin | Splits text into sentences. |
| Named Entity Recognition | TokenNameFinder | en-ner-person.bin | Finds named entities. |
| POS Tagging | POSTagger | en-pos-maxent.bin | Assigns POS tags to tokens. |
The CLI provides an accessible and efficient way to leverage the power of OpenNLP, complementing the deep integration capabilities of the Java API.