How would I get the distance of the closest player from a certain player?

This just does my head in when I try and think about how to do it, I understand I would have to cycle through all the characters in the workspace, getting their distances and comparing them to see which is the lowest then getting the closest character and constantly refreshing every amount of time to live track them but I have no idea on how to write it out as a script. Could someone explain to me how this would be done?