how to detect how much a video has downloaded in youtube-dl code example

Example 1: youtubedl best quality

youtube-dl -f best https://www.youtube.com/watch?v=nYdiDq1fOiM

Example 2: downloading youtube playlists using youtube-dl in highest quality

youtube-dl -f best 'http://www.youtube.com/watch?v=P9pzm5b6FFY'