The check.txt is the contents of the webpage, you can use curl -o to take all the webpage contents from the nerd fonts https://www.nerdfonts.com/ and save it as text and then you can use the first command to save the contents from the page to all_fonts.txt and then use the second line to install the font which you like.
Gaurav
Academic Staff Member
Bioinformatics
Institute for Biochemistry and Biology
University of Potsdam
Potsdam,Germany