32  sudo apt install vim
   33  vim
   34  ls
   35  python hello.py
   36  vim hello.py
   37  wc hello.py
   38  wc -l hello.py
   39  vim
   40  ls
   41  cat hello.py linear.py > hello_linear.py
   42  ls
   43  python hello_linear.py
   44  cat hello_linear.py