stanfordnlp/CoreNLP · error · IllegalArgumentException

Please specify -output

Error message

Please specify -output

What it means

IllegalArgumentException from ConvertModels.main when the -model argument is absent or not one of SENTIMENT, DVPARSER, EMBEDDING, COREF, FASTCOREF, or when -input/-output paths are missing; these flags are mandatory for model conversion.

Solutions

1. Add -output /path/to/destination/model to the command
2. Fix the flag spelling so argsToProperties sees 'output'
3. Quote paths containing spaces on the command line

Example fix

// before
... -stage NEW -model SENTIMENT -input models/sentiment.ser.gz
// after
... -stage NEW -model SENTIMENT -input models/sentiment.ser.gz -output models/sentiment-new.ser.gz

if (outputArg == null || outputArg.isBlank()) {
  throw new IllegalArgumentException("-output must be a non-empty path");
}

try {
  ConvertModels.main(args);
} catch (IllegalArgumentException e) {
  if (e.getMessage().equals("Please specify -output")) {
    System.err.println("Missing -output; usage: -input <modelPath> -output <modelPath>");
    System.exit(2);
  }
  throw e;
}

When it happens

Trigger: Running the converter without -output, or misspelling the flag so the property key 'output' is missing.

Common situations: Omitting the destination when scripting batch conversions, or shell-quoting issues swallowing the argument.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Please specify -input
• Please specify -model, either SENTIMENT, DVPARSER…
• Please specify -stage, either OLD or NEW
• Conflicting properties. Multi-word rules file will be…
• Must specify a treebank to train from with -trainTreebank…

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/5086b5147423ae41. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/neural/ConvertModels.java:394

    try {
      stage = Stage.valueOf(props.getProperty("stage").toUpperCase(Locale.ROOT));
    } catch (IllegalArgumentException | NullPointerException e) {
      throw new IllegalArgumentException("Please specify -stage, either OLD or NEW");
    }

    final Model modelType;
    try {
      modelType = Model.valueOf(props.getProperty("model").toUpperCase(Locale.ROOT));
    } catch (IllegalArgumentException | NullPointerException e) {
      throw new IllegalArgumentException("Please specify -model, either SENTIMENT, DVPARSER, EMBEDDING, COREF, FASTCOREF");
    }

    if (!props.containsKey("input")) {
      throw new IllegalArgumentException("Please specify -input");
    }

    if (!props.containsKey("output")) {
      throw new IllegalArgumentException("Please specify -output");
    }

    String inputPath = props.getProperty("input");
    String outputPath = props.getProperty("output");

    if (modelType == Model.SENTIMENT) {
      if (stage == Stage.OLD) {
        SentimentModel model = SentimentModel.loadSerialized(inputPath);
        ObjectOutputStream out = IOUtils.writeStreamFromString(outputPath);
        writeSentiment(model, out);
        out.close();
      } else {
        ObjectInputStream in = IOUtils.readStreamFromString(inputPath);
        SentimentModel model = readSentiment(in);
        in.close();
        model.saveSerialized(outputPath);
      }
    } else if (modelType == Model.DVPARSER) {

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