Object which can be executed as a "main program" or "subcommand"

Certain peak.running facilities require the use of an "executable" object. Executable objects are objects which implement one of the following interfaces (listed in descending preference order):

• ICmdLineAppFactory - supports I/O redirection, environment override, command line arguments, and returned exit level

• IRerunnable - supports I/O redirection, environment override, command line arguments, and returned exit level

• ICmdLineApp - redirection and overrides are attempted via sys and os but not guaranteed to work; run() return value is used as exit level.

• Any object callable with no arguments; redirection and overrides are attempted via sys and os but not guaranteed to work; return value of called object used as exit level.

Objects which implement any of these interfaces can be invoked as subcommands by peak.running.commands classes like Bootstrap and IniInterpreter. Notice that callables and ICmdLineApp instances can't be completely controlled by their invoker, so if you want to create a component that can have its I/O redirected by a controlling component, you should create an IRerunnable or ICmdLineAppFactory.

Note that IExecutable is an "abstract interface" for documentation purposes only. Declaring that you implement IExecutable directly is meaningless; you must implement one of the three explicit sub-interfaces or be a callable object to be "executable".