ARGS4J

args4j is a simple library for parsing command-line arguments for Java 8+.

Quickstart

To parse command line arguments, simply use:

public static void main(String[] args) {
    List<Token> tokens=Args.parse(args);
}

For example, in the above code, the commented list of program arguments would result in the following token objects:

// -a -abc --alpha --alpha=bravo - -- charlie --delta -echo
Arrays.asList(
    new SwitchNameToken(SwitchName.of("a"), false),
    new SwitchNameToken(SwitchName.of("a"), false),
    new SwitchNameToken(SwitchName.of("b"), true),
    new SwitchNameToken(SwitchName.of("c"), true),
    new SwitchNameToken(SwitchName.of("alpha"), false),
    new SwitchNameToken(SwitchName.of("alpha"), false),
    new ValueToken("bravo", true),
    new ValueToken("-", false),
    new ValueToken("charlie", false),
    new ValueToken("--delta", false),
    new ValueToken("-echo", false));

Dialects

The Dialect object creates the ArgTokenizer object that the ArgsParser object uses to convert program arguments into Token objects.

Users can specify a Dialect like this:

public static void main(String[] args) {
    List<Token> tokens=Args.parse(UnixDialect.INSTANCE, args);
}

If users do not specify a dialect, then the UnixDialect is used.

Unix Dialect

The default Unix dialect supports the following syntax:

• Long Switch:

  • A command-line argument that begins with -- followed by a name.
  • Example: --alpha
  • Represents an option or setting with a descriptive name.

• Long Switch with Attached Value:

  • A long switch followed by an = and its associated value.
  • Example: --alpha=bravo
  • Combines a switch and its value in a single token.

• Short Switch:

  • A single-character switch prefixed with -.
  • Example: -a
  • Provides a shorthand for enabling options.

• Short Switch Batch:

  • A single argument starting with -, followed by multiple single-character switches concatenated together.
  • Example: -abc
  • Represents multiple short switches: -a, -b, and -c.

• Separator:

  • A meta-token represented by --, which forces all subsequent arguments to be treated as values, even if they look like switches.
  • Example: --
  • Ensures arguments like --delta and -echo are treated as value tokens.

• Value:

  • Any other token
  • Example: alpha
  • Represents the actual data passed to applications

MS/DOS Dialect

The MS/DOS dialect supports the following syntax:

• Switch:

  • A command-line argument that begins with / followed by a name.
  • Examples: /a, /alpha
  • Represents an option or setting.

• Value:

  • An argument that does not start with / and is treated as a value rather than a switch.
  • Example: value
  • Represents data or parameters passed to the command.

Other Dialects

Users are free to implement their own Dialect objects. See UnixDialect and MsDosDialect for examples.