Download YouTube videos from command line
You can now save your favorite videos from YouTube to your hard disk by using youtube-dl, a small command-line program to download videos from YouTube. It requires the Python interpreter 2.4 or later and it is platform independent (should work on linux, windows, mac, etc).
To install youtube-dl, you should put the python script under PATH, I recommend putting it inside /usr/local/bin. Once youtube-dl is inside your PATH, you should be able to access the script by typing youtube-dl.
To download video from youtube.com type:
youtube-dl http://youtube.com/watch?v=dMH0bHeiRNg
The above command will download and save the video on your hard drive in flv format. Good luck!