I've written a quick script to print the network interface speeds, designed for use with GeekTool. In particular, this is very useful for seeing how fast your WiFi has connected. Create a new entry in GeekTool, and set it to a Shell action (how to do this varies depending on if you're using GeekTool 2.x or 3.x). In the Command window, enter the following code:
Set the Refresh pop-up to whatever you prefer; the information provided is generally unchanging, so you can use a large refresh interval. If you'd prefer to run the above as a straight shell script, change the echo lines at the end to be echo -e .... Note that the script assumes en0 is wired Ethernet, and en1 is wireless networking.Mac OS X Hints
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