CUD Cursor Down

Move the cursor Pn lines down, keeping its column. A 0 is taken as 1.

The cursor stops at the bottom margin if it started at or above it. A cursor already below the bottom margin stops at the last line instead. CUD never scrolls, which is the difference between it and a line feed: at the bottom margin a line feed scrolls the region up, and CUD stays put.

Moving the cursor cancels any pending wrap. DEC STD 070 calls the pending wrap the Last Column Flag, and its appendix on autowrap lists this among the controls that should reset it (§D.6.1, p. D-13); xterm clears it in CursorDown, and libghostty-vt does the same.

CUU goes the other way, and CNL moves down and returns to the left margin as well.

Validation

CUD-1: Down one line

\e[1;2H
\e[B
X

|_____|
|_X___|
|_____|

CUD-2: Down n lines, stopping at the last line

\e[1;2H
\e[9B
X

|_____|
|_____|
|_X___|

CUD-3: Stops at the bottom margin, without scrolling

A
\e[1;3r   # region is lines 1 to 3
\e[2;1H
\e[9B
X

|A____|
|_____|
|X____|
|_____|

CUD-4: Below the bottom margin

\e[1;2r   # region is lines 1 and 2
\e[3;1H   # below it
\e[9B
X

|_____|
|_____|
|_____|
|X____|

CUD-5: From a pending wrap

ABCDE     # fills the line; a wrap is pending
\e[B
X

|ABCDE|
|____X|
|_____|