Clad User Manual - Concepts
Internal
Default Command
An application may not have a default command. In this case, the ApplicationRuntime implementation of public String getDefaultCommand() must return null.
Options
The options (global or specific to a certain command) use the GNU command line option syntax:
-o <value> | --option=<value>
Global Options
The global options apply to the application runtime, and they are not specific to a certain command.
Universal Global Options
All clad-based application automatically support the following global options. There is no need to declared them among the "required" or "optional" global options for a specific application.
-v|--verbose
-v or --verbose turn on DEBUG on the underlying CONSOLE appender, so the application will display internal execution information at stdout. In order to be displayed in this mode, the internal execution information must be logged by the application with SLFJ4 debug() method. For more details on how to program debug logging, see How to Implement a Command Line Application - Debug Logging.
-d|--debug
-d or --debug, in addition to logging debug information at the CONSOLE the way -v|--verbose options do, start the underlying JVM in debug mode, so a debugger can be attached to it.
Command Options
Logging
Error Handling
If a processing error is caused by what the user did, or by the input data, and it can be corrected by user input (or by data correction), throw an UserErrorException with a human-readable message. The upmost runtime layer must be designed so it displays the error message at stderr and System.exit()s.
Configuration File
Each command line option has a configuration file correspondent. Command line value takes precedence over the configuration file value.