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:

• CommandGroup
• CommandDispatcher
• CommandSession

Method Summary

Modifier and Type	Method	Description
default List<String>	aliases()	Returns alternative names for this command.
default Completer	completer()	Returns a single completer for this command's arguments.
default List<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<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()

completer

default 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:

• completers()

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