Linux Sorting Contents of Multiple Files in a Single File

 https://www.tecmint.com/13-basic-cat-command-examples-in-linux/

13. Sorting Contents of Multiple Files in a Single File

This will create a file test4 and the output of the cat command is piped to sort and the result will be redirected to a newly created file.

# cat test test1 test2 test3 | sort > test4