This chapter deals with screen input and output that is not
pixel based, but character based. When we say character, we mean
a composition of pixels that can be changed depending on a charset.
Your graphic card already offers one or more charsets and operates
by default in text (charset) mode because text can be processed
much faster than pixel graphic. There is more to do with terminals
than to use them as simple (dumb) and boring text displays. I will
describe how to use the special features that your linux terminal,
especially the linux console, offers.
printf, sprintf, fprintf, scanf, sscanf, fscanf
With these functions from you can output formatted
strings to (standard output),
(standard error) or other streams defined as FILE *stream (files,
for example). Scanf(...) provides a similar way to read
formatted input from .
termcap
The TERMinal CAPabilitie database is a set of terminal
description entries in the ASCII file /etc/termcap. Here you
can find information about how to display special characters,
how to perform operations (delete, insert characters or lines
etc) and how to initialize a terminal. The database is used,
for example, by the editor vi. There are view library functions
to read and use the terminal capabilities (termcap(3x)).
With this database, programs can work with a variety of
terminals with the same code. Using the termcap database and
library functions provides only low level access to the
terminal. Changing attributes or colors, parameterized output
and optimization must be done by the programmer himself.
terminfo database
The TERMinal INFOrmation database is based on the termcap
database and also describes terminal capabilities, but on a
higher level than termcap. Using terminfo, the program can
easily change screen attributes, use special keys such as
function keys and more. The database can be found in
/usr/lib/terminfo/[A-z,0-9]*. Every file describes one
terminal.
curses
Terminfo is a good base to use for terminal handling in a
program. The (BSD-)CURSES library gives you
high level access to the terminal and is based on the terminfo
database. Curses allows you to open and manipulate windows on
the screen, provides a complete set of input and output
functions, and can alter video attributes in a terminal
independent manner on more than 150 terminals. The curses
library can be found in /usr/lib/libcurses.a.
This is the BSD version of curses.
ncurses
Ncurses is the next improvement. In version 1.8.6 it should be
compatible with AT&T curses as defined in SYSVR4 and has some
extensions such as color manipulation, special optimization for
output, terminal specific optimizations, and more. It has been
tested on a lot of systems such as Sun-OS, HP and Linux.
I recommend using ncurses instead of the others. On SYSV Unix
systems (such as Sun's Solaris) there should exist a curses
library with
the same functionality as ncurses (actually the solaris curses
has some more functions and mouse support).
In the following sections I will describe how to use the
different packages to access a terminal. With Linux we have the
GNU-version of termcap and we can use ncurses instead of
curses.
