Run a file with arguments using grunt

I have a file called file_1.js which accepts an argument. So i run the file using

"#casperjs file_1.js myarg"

Now I have put the file to run automacitally as a task. Now I run it as

"#grunt casperjs" which runs file_1.js.

But how do I pass my argument for file_1.js and still make it run with grunt?

You could use the grunt-casper task if it has the options you need, otherwise you could use grunt-shell to run the command.