Download youtube videos in ubuntu terminal in any format and with any ubuntu version

1) First you have to install youtube-dl in ubuntu for that
  type command : sudo apt-get install youtube-dl      
 and press enter.

2) For download any video from youtube
  type command:youtube-dl -o filename youtube_video_link
  like youtube-dl -o rodiesx1 https://www.youtube.com/watch?v=RXNesSIFWyM
and press enter
 3) you can insert -f for different format 
  like youtube-dl -f 34 -o rodiesx1 https://www.youtube.com/watch?v=RXNesSIFWyM
   after -f what number is given that are the file format you have to specify...
 To know the number of all other format 
type command: youtube-dl --help
 There you can get all the other video format number specified...
 enjoy .........:)