Question: I want to download any videos form any site using terminal command , I know "`youtube-dl`" but it doesn't download videos from some sites like khan academy so, what is the best for that ?

Answer: 
You can also use `youtube-dl` for that. Just copy the url of the video. In case you don't know about the link. Just right click & see **View Frame Info** you'll see the video url there. Then

```
youtube-dl videourl

```
You can use movgrab.

To install Movgrab:

```
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install movgrab

```

Check [this](http://www.webupd8.org/2012/02/movgrab-command-line-video-downloader.html) for more information

Or you can download the source, extract it and compile it:

```
 wget https://sites.google.com/site/columscode/files/movgrab-1.2.1.tar.gz
 tar xvf movgrab-1.2.1.tar.gz
 cd movgrab-1.2.1/
 ./configure
 make
 sudo make install

```