How do I open a text file from a terminal window from within the Android GUI?

I'm trying to open a text file from within a terminal window emulator -- but not so it opens in the actual terminal but more like I've just clicked on it. So my question is: What command can I use to open /mnt/sdcard/textfile.txt from a terminal window emulator from ROM Toolbox Lite within the Android GUI so that it will open with any one of my text editing applications? Will I need to run su before I can run what ever command? I'd prefer not to, but the device is rooted so I can run su. I'm using Android version 4.0.4.