How can I tell Chrome or Firefox to run Javascript or load a Bookmarklet from the commandline?

Is it possible to, from the command line, tell Chrome or Firefox to run javascript i开发者_StackOverflow社区n the currently open browser window? Or alternatively, load a bookmarklet that contains javascript?

I'd like to have a program that watches for changes to a css file, and when the css file updates, the browser window would automatically load the new css file. I've setup a javascript bookmarklet to do this, but I'd love to have it done automatically whenever the css file updates.

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In Firefox this definitely won't be possible without an extension, don't know about Chrome. The command line can open a javascript: URL but this code will run in its own tab, without access to the page you are currently viewing. So an extension would need to implement nsICommandLineHandler interface (see https://developer.mozilla.org/en/Chrome/Command_Line for an example) and handle some command line flag. It would then use nsIWindowWatcher.getMostRecentWindow("navigator:browser") to get the current browser window and do window.gBrowser.contentWindow.location.href = "javascript:..." to run the bookmarklet on the current tab.

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For FF: The source code to this may help: https://addons.mozilla.org/en-US/firefox/addon/css-refresh-199425/