Module org.jline.shell
Package org.jline.shell

Interface Command

All Known Implementing Classes:
AbstractCommand
public interface Command
Represents a single executable command in the shell.

A Command encapsulates everything about a command in one object: its name, aliases, description, execution logic, and completion support.

Example: 

 Command echo = new AbstractCommand("echo") {
     @Override
     public Object execute(CommandSession session, String[] args) {
         session.out().println(String.join(" ", args));
         return null;
     }
 };
Since:
4.0
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    default List<String>
    aliases()
    Returns alternative names for this command.
    default org.jline.reader.Completer
    completer()
    Returns a single completer for this command's arguments.
    default List<org.jline.reader.Completer>
    completers()
    Returns the completers for this command's arguments.
    default CommandDescription
    describe(List<String> args)
    Returns a detailed description of this command for the given arguments.
    default String
    description()
    Returns a short, one-line description of this command.
    Object
    execute(CommandSession session, String[] args)
    Executes this command with the given session and arguments.
    String
    name()
    Returns the primary name of this command.
    default Map<String,Command>
    subcommands()
    Returns the subcommands of this command.

  • Method Details

    • name

      String name()
      Returns the primary name of this command.
      Returns:
      the command name, never null

    • aliases

      default List<String> aliases()
      Returns alternative names for this command.

      The default implementation returns an empty list.

      Returns:
      the list of aliases, never null

    • description

      default String description()
      Returns a short, one-line description of this command.

      Used for help listings and completion candidates.

      Returns:
      the description, or empty string if none

    • describe

      default CommandDescription describe(List<String> args)
      Returns a detailed description of this command for the given arguments.

      This is used by widgets to display context-sensitive help in the terminal status bar.

      Parameters:
      args - the command arguments (args[0] is typically the command name)
      Returns:
      the command description, or null if not available

    • execute

      Object execute(CommandSession session, String[] args) throws Exception
      Executes this command with the given session and arguments.
      Parameters:
      session - the current command session
      args - the command arguments (does not include the command name)
      Returns:
      the result of the command execution, or null
      Throws:
      Exception - if command execution fails

    • completers

      default List<org.jline.reader.Completer> completers()
      Returns the completers for this command's arguments.

      The default implementation returns an empty list, meaning no custom completion.

      These completers are position-based: the first completer handles the first argument, the second handles the second argument, etc. For commands that need non-positional completion (e.g., picocli commands where options can appear in any order), override completer() instead.

      Returns:
      the list of completers
      See Also:

    • completer

      default org.jline.reader.Completer completer()
      Returns a single completer for this command's arguments.

      This method is called by the dispatcher to get the completer for this command. The default implementation builds a completer from completers().

      Override this method when position-based completion is not appropriate, for example with picocli commands where options and arguments can appear in any order.

      Returns:
      the completer, or null for no completion
      See Also:

    • subcommands

      default Map<String,Command> subcommands()
      Returns the subcommands of this command.

      When a command has subcommands, the dispatcher will check if the first argument matches a subcommand name and route execution accordingly. For example, a "git" command with a "commit" subcommand would handle git commit -m msg by routing to the "commit" subcommand with args [-m, msg].

      The default implementation returns an empty map, meaning no subcommands.

      Returns:
      a map from subcommand name to command, never null