[Blikkentrekker]

They are simply em-dashes, if an error should occur, they are replaced with numbers to indicate the error code; they are also color-coded to indicate when I'm not for instance in an SSH session by changing to another color:

  —— — true
  —— — false
  —— 1 sh -c 'exit 120'
   120 sh -c 'exit 20'
  — 20

It doesn't show the colors here of course.