How to download a video from youtube on linux using command line:

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1/ Install the package " youtube-dl " by the command ( sudo apt-get install youtube-dl or sudo zypper youtube-dl )
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2/ Then open terminal and type:
youtube-dl -f video url
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The -f flag is used to list out all the available formats and resolution of the video against some numbers. In this example, the highest resolution is (1280×720) is defined by the number 22.
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We will download in this resolution by typing
youtube-dl -f 22 “video url”
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3/ Example:
youtube-dl -f 22 https://www.youtube.com/watch?v=71CykvkugUg