open opens a file in its default application, using the appropriate tool for the
operating system. On GNU/Linux, this requires the common but optional xdg-open
utility, from the xdg-utils package.
Note that this function will not be used if a command by this name exists (which
is the case on macOS or Haiku).
open *.txt opens all the text files in the current directory using your system's
default text editor.