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Reference tt CLI utility Extending the tt functionality

Extending the tt functionality

The tt utility implements a modular architecture: its commands are, in fact, separate modules. When you run tt with a command, the corresponding module is executed with the given arguments.

The modular architecture enables the option to extend the tt functionality with external modules (as opposed to internal modules that implement built-in commands). Simply said, you can write any code you want to execute from tt, pack it into an executable, and run it with a tt command:

tt my-module-name my-args

The name of the command that executes a module is the same as the name of the module’s executable.

Executables that implement external tt modules must have two flags:

  • --description – print a short description of the module. The description is shown alongside the command in the tt help.
  • --help – display help. The help message is shown when tt help <module_name> is called.

External modules must be located in the modules directory specified in the configuration file:

tt:
  modules:
    directory: path/to/modules/dir

To check if a module is available in tt, call tt help. It will show the available external modules in the EXTERNAL COMMANDS section together with their descriptions.

External modules can overload built-in tt commands. If you want to change the behavior of a built-in command, create an external module with the same name and your own implementation.

When tt sees two modules – an external and an internal one – with the same name, it will use the external module by default.

For example, if you want tt to show the information about your Tarantool application, write the external module version that outputs the information you need. The tt version call will execute this module instead of the built-in one:

tt version # Calls the external module if it's available

You can force the use of the internal module by running tt with the --internal or -I argument. The following call will execute the built-in version even if there is an external module with the same name:

tt version -I # Calls the internal module
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