The deleteln and wdeleteln routines delete the line under the cursor in the window; all lines below the current line are moved up one line. The bottom line of the window is cleared. The cursor position does not change.
The insdelln and winsdelln routines, for positive n, insert n lines into the specified window above the current line. The n bottom lines are lost. For negative n, delete n lines (starting with the one under the cursor), and move the remaining lines up. The bottom n lines are cleared. The current cursor position remains the same.
The insertln and winsertln routines, insert a blank line above the current line and the bottom line is lost.
All routines return the integer ERR upon failure and an OK (SVr4 specifies only "an integer value other than ERR") upon successful completion.
These functions are described in the XSI Curses standard, Issue 4. The standard specifies that they return ERR on failure, but specifies no error conditions.
Note that all but winsdelln may be macros.
These routines do not require a hardware line delete or insert feature in the terminal. In fact, they wont use hardware line delete/insert unless idlok(..., TRUE) has been set on the current window.