Here's the shortest I've gotten after looking at some of the comments:
IO.write$*.pop,ARGF.lines.sort.join
And yes, it does work even without the space between `write` and `$*`.
Also after testing, I realized the ('\n') is not required for join. When you call 'lines', it still has the '\n' character in the string, and when you join, it defaults to join without a delimiter, so it's putting them back together with the newline still there.
Also after testing, I realized the ('\n') is not required for join. When you call 'lines', it still has the '\n' character in the string, and when you join, it defaults to join without a delimiter, so it's putting them back together with the newline still there.