The initscr code determines the terminal type and initializes all curses data structures. initscr also causes the first call to refresh(3X) to clear the screen. If errors occur, initscr writes an appropriate error message to standard error and exits; otherwise, a pointer is returned to stdscr.
A program that outputs to more than one terminal should use the newterm
routine for each terminal instead of initscr.
A program that needs to inspect capabilities,
so it can continue to run in a line-oriented mode if the
terminal cannot support a screen-oriented program, would also use
The routine newterm should be called once for each terminal.
It returns a variable of type SCREEN * which should be saved
as a reference to that terminal.
newterm's arguments are
.IP • 4 the type of the terminal to be used in place of $TERM,
.IP • 4 a file pointer for output to the terminal, and
.IP • 4 another file pointer for input from the terminal
The program must also call endwin for each terminal being used before exiting from curses. If newterm is called more than once for the same terminal, the first terminal referred to must be the last one for which endwin is called.
A program should always call endwin before exiting or escaping from
curses mode temporarily.
.IP • 4 resets colors to correspond with the default color pair 0,
.IP • 4 moves the cursor to the lower left-hand corner of the screen,
.IP • 4 clears the remainder of the line so that it uses the default colors,
.IP • 4 sets the cursor to normal visibility (see curs_set(3X)),
.IP • 4 stops cursor-addressing mode using the exit_ca_mode terminal capability,
.IP • 4 restores tty modes (see reset_shell_mode(3X)).
The set_term routine is used to switch between different terminals. The screen reference new becomes the new current terminal. The previous terminal is returned by the routine. This is the only routine which manipulates SCREEN pointers; all other routines affect only the current terminal.
The delscreen routine frees storage associated with the SCREEN data structure. The endwin routine does not do this, so delscreen should be called after endwin if a particular SCREEN is no longer needed.
Routines that return pointers always return NULL on error.
X/Open defines no error conditions.
In this implementation
.IP • 4 endwin returns an error if the terminal was not initialized.
.IP • 4 newterm returns an error if it cannot allocate the data structures for the screen, or for the top-level windows within the screen, i.e., curscr, newscr, or stdscr.
.IP • 4 set_term returns no error.
Old versions of curses, e.g., BSD 4.4, may have returned a null pointer from initscr when an error is detected, rather than exiting. It is safe but redundant to check the return value of initscr in XSI Curses.
If the TERM variable is missing or empty, initscr uses the value ``unknown'', which normally corresponds to a terminal entry with the generic (gn) capability. Generic entries are detected by setupterm (see curs_terminfo(3X)) and cannot be used for full-screen operation. Other implementations may handle a missing/empty TERM variable differently.
Quoting from X/Open Curses, section 3.1.1:
Curses implementations may provide for special handling of the SIGINT, SIGQUIT and SIGTSTP signals if their disposition is SIG_DFL at the time initscr is called ...
Any special handling for these signals may remain in effect for the life of the process or until the process changes the disposition of the signal.
None of the Curses functions are required to be safe with respect to signals ...
This implementation establishes signal handlers during initialization, e.g., initscr or newterm. Applications which must handle these signals should set up the corresponding handlers after initializing the library: