This DrRacket plugin adds a text field to DrRacket for inputting command-line arguments. The command-line arguments then will be available via the parameter current-command-line-arguments.
Note that it requires users to run a program for a change to take its effect in the interactions window.
The current limitation of this plugin is that it only works with #lang languages. It will not work with HtDP languages, for example. The background color of the text field will turn yellow to warn that the command-line arguments have no effect in this case.
When there is a syntax error (unterminated quote or escape code), the background color of the text field will turn red, and current-command-line-arguments will be set to #().