Reverse Index (RI)

Move the cursor up one cell, scrolling if necessary.

  1. 0x1B
    ESC
  2. 0x4D
    M

This sequence does not unset the pending wrap state.

If the cursor is exactly on the top margin and is within left and right margins, invoke scroll down (SD) with n = 1. The operation is complete.

Otherwise, scrolling isn't necessary. Perform a cursor up operation with n = 1.

Validation

RI V-1: No Scroll Region, Top of Screen

printf "\033[1;1H" # move to top-left
printf "\033[0J" # clear screen
printf "A\n"
printf "B\n"
printf "C\n"
printf "\033[1;1H" # move to top-left
printf "\033M" # reverse index
printf "X"
|Xc________|
|A_________|
|B_________|
|C_________|

RI V-2: No Scroll Region, Not Top of Screen

printf "\033[1;1H" # move to top-left
printf "\033[0J" # clear screen
printf "A\n"
printf "B\n"
printf "C\n"
printf "\033[2;1H"
printf "\033M" # reverse index
printf "X"
|Xc________|
|B_________|
|C_________|

RI V-3: Top/Bottom Scroll Region

printf "\033[1;1H" # move to top-left
printf "\033[0J" # clear screen
printf "A\n"
printf "B\n"
printf "C\n"
printf "\033[2;3r" # scroll region
printf "\033[2;1H"
printf "\033M" # reverse index
|A_________|
|c_________|
|B_________|

RI V-4: Outside of Top/Bottom Scroll Region

printf "\033[1;1H" # move to top-left
printf "\033[0J" # clear screen
printf "A\n"
printf "B\n"
printf "C\n"
printf "\033[2;3r" # scroll region
printf "\033[1;1H"
printf "\033M" # reverse index
|A_________|
|B_________|
|C_________|

RI V-5: Left/Right Scroll Region

printf "\033[1;1H" # move to top-left
printf "\033[0J" # clear screen
printf "ABC\n"
printf "DEF\n"
printf "GHI\n"
printf "\033[?69h" # enable left/right margins
printf "\033[2;3s" # scroll region left/right
printf "\033[1;2H"
printf "\033M"
|A_________|
|DBC_______|
|GEF_______|
|_HI_______|

RI V-6: Outside Left/Right Scroll Region

printf "\033[1;1H" # move to top-left
printf "\033[0J" # clear screen
printf "ABC\n"
printf "DEF\n"
printf "GHI\n"
printf "\033[?69h" # enable left/right margins
printf "\033[2;3s" # scroll region left/right
printf "\033[2;1H"
printf "\033M"
|ABC_______|
|DEF_______|
|GHI_______|

Cursor on the A.