1. Redirect stdout to one file and stderr to another file:
   
   Ruby

   command > out 2>error

   1 2	command > out 2>error

2. Redirect stderr to stdout (&1), and then redirect stdout to a file:
   
   Ruby

   command >out 2>&1

   1 2	command >out 2>&1

3. Redirect both to a file:
   
   Ruby

   command &> out

   1	command &> out

https://askubuntu.com/questions/625224/how-to-redirect-stderr-to-a-file