stanfordnlp/CoreNLP · error · RuntimeException

Unknown argument " + args[argIndex]

Error message

Unknown argument " + args[argIndex]

What it means

PrintTagList is a small command-line tool for printing tag lists from a parser model. Its main() loops over CLI arguments and throws RuntimeException when it encounters any flag other than the recognized ones (like -model). The thrown message wraps the unrecognized argument verbatim.

Solutions

1. Check the printed message for the offending argument and fix the typo or remove the token
2. Prefix the model file path with -model (required: the tool exits with code 2 if parserFile is null)
3. Run with no arguments or inspect main() source to list supported flags
4. Re-check the tool invocation in your script; note log.info also prints the same message before throwing

Example fix

// before
java PrintTagList -modelfile parserModel.ser.gz
// after
java PrintTagList -model parserModel.ser.gz

// validate args before invoking main
Set<String> allowed = Set.of("-model");
for (int i = 0; i < args.length; i++) {
  if (!allowed.contains(args[i]))
    throw new IllegalArgumentException("Unsupported flag: " + args[i]);
  i++; // skip value
}
if (args.length == 0 || !List.of(args).contains("-model"))
  throw new IllegalArgumentException("-model is required");

try {
  PrintTagList.main(args);
} catch (RuntimeException e) {
  if (e.getMessage().startsWith("Unknown argument")) {
    System.err.println("Bad flag: " + e.getMessage());
  } else throw e;
}

When it happens

Trigger: Running PrintTagList with an unrecognized command-line flag, e.g. `java edu.stanford.nlp.parser.tools.PrintTagList -modelfile x` (typo) or with a stray positional token such as a filename passed without a flag.

Common situations: Typos in flag names, using flags from a different Stanford tool, passing a model path without the -model prefix, shell quoting issues leaving stray tokens in args.

Understand the failure class

Background: "Unknown argument", "Invalid value", and "must be one of": invalid CLI argument errors explained — this error's family across 35 libraries.

Related errors

• Unknown argument:
• Unknown argument " + args[argIndex]
• Unknown argument
• Unknown argument
• Unknown argument

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/e1fe6d65643c9cc8. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/parser/tools/PrintTagList.java:28

/**
 * Loads a LexicalizedParser and tries to get its tag list.
 *
 * @author John Bauer
 */
public class PrintTagList  {

  /** A logger for this class */
  private static Redwood.RedwoodChannels log = Redwood.channels(PrintTagList.class);
  public static void main(String[] args) {
    String parserFile = null;
    for (int argIndex = 0; argIndex < args.length; ) {
      if (args[argIndex].equalsIgnoreCase("-model")) {
        parserFile = args[argIndex + 1];
        argIndex += 2;
      } else {
        String error = "Unknown argument " + args[argIndex];
        log.info(error);
        throw new RuntimeException(error);
      }
    }
    if (parserFile == null) {
      log.info("Must specify a model file with -model");
      System.exit(2);
    }

    LexicalizedParser parser = LexicalizedParser.loadModel(parserFile);

    Set<String> tags = Generics.newTreeSet();
    for (String tag : parser.tagIndex) {
      tags.add(parser.treebankLanguagePack().basicCategory(tag));
    }
    System.out.println("Basic tags: " + tags.size());
    for (String tag : tags) {
      System.out.print("  " + tag);
    }
    System.out.println();

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