To summarize, if you type scala on the command line without a file argument, the interpreter runs in interactive mode.
总的来说，如果你在命令行输入scala 而不输入文件名参数，解释器会运行在交互模式。
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Following the example of the execution of the argument CMD, you could write a shell or interactive environment in Rexx (perhaps running either external utilities or built-in commands, much like bash).
If you provide a filename as an argument, the monkeyrunner command runs the file's contents as a Python program; otherwise, it starts an interactive session.