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 use `wget` for that. 

type the following command on terminal:

```
 apt­-get install wget

```

Download a single file using wget.

```
 wget "your video url link"

```
You could use this:

```
wget --force-yes "'echo$http:url'" 

```

and it might work fine this way.