This is a description of how to actually use the screen package.For simplicity, we assume all updating, reading, etc. is applied
to although a different window can of course be specified. In
order to use the screen package, the routines must know about
terminal characteristics, and the space for and must be allocat‐
ed. These functions are performed by Since it must allocate
space for the windows, it can overflow core when attempting to do
so. On this rather rare occasion, returns ERR. must be called
before any of the routines which affect windows are used. If it
is not, the program will core dump as soon as either or are ref‐
erenced. However, it is usually best to wait to call it until
after you are sure you will need it, like after checking for
startup errors. Terminal status changing routines like and
should be called after After the initial window allocation done
by specific window characteristics can be set. Scrolling can be
enabled by calling If you want the cursor to be left after the
last change, use If this isn’t done, will move the cursor to the
window’s current after updating it. Additional windows can be
created by using the functions and allows you to delete an ex‐
isiting window. The variables and control the size of the termi‐
nal. They are initially implicitly set by but can be altered ex‐
plicitly by the user followed by a call to Note that any call towill always delete any existing and/or before creating new ones
so this change is best done before the initial call to The basicfunctions used to change what will go on a window are and adds acharacter at the current , returning ERR if it would cause the
window to illegally scroll, printing a character in the lower
right‐hand corner of a terminal which automatically scrolls if
scrolling is not allowed. changes the current to whatever youwant them to be. It returns ERR if you try to move off the win‐
dow. As mentioned above, you can combine the two into to do both
things in one call. The other output functions (such as and allcall to add characters to the window. After a change has beenmade to the window, you must call when you want the portion of
the terminal covered by the window to reflect the change. In or‐
der to optimize finding changes, assumes that any part of the
window not changed since the last of that window has not been
changed on the terminal, that you have not refreshed a portion of
the terminal with an overlapping window. If this is not the
case, the routines and are provided to make it look like a de‐
sired part of window has been changed, thus forcing to check that
whole subsection of the terminal for changes. If you call withit will make the screen look like the image of This is useful forimplementing a command which would redraw the screen in case it
got messed up. Input is essentially a mirror image of output.The complementary function to is which, if echo is set, will call
to echo the character. Since the screen package needs to knowwhat is on the terminal at all times, if characters are to be
echoed, the tty must be in raw or cbreak mode. If it is not,
sets it to be cbreak, and then reads in the character. In order
to perform certain optimizations, and, on some terminals, to work
at all, some things must be done before the screen routines start
up. These functions are performed in and which are called by Inorder to clean up after the routines, the routine is provided.
It restores tty modes to what they were when was first called.The terminal state module uses the variable to save the original
terminal state which is then restored upon a call to Thus, any‐
time after the call to initscr, should be called before exiting.
Note however, that should always be called the final calls to
which free the storage of the windows.
