Send a request to the website random.org to generate one string of 20 characters containing both upper and lower case letters and numbers, and remove any non-alphanumeric characters from the output.
curl -s https://www.random.org/strings/?num=1\&len=20\&digits=on\&upperalpha=on\&loweralpha=on\&unique=on\&format=plain\&rnd=new | sed 's/[^a-zA-Z0-9]//g'