7.4
116 Chapter 7: Running X Clients
X by itself is incompatible with all character-based applications. The X server does
not provide a termios interface and cannot be configured to understand the types of
control codes emitted by curses.
In order to bridge this gulf and use character-based programs with X, it is necessary
to use a two-sided application that presents a termios interface on one side and is a
client to an X server on the other side. This application must translate incoming X
events: keypress events are translated into ASCII sequences, window closure is translated
into a modem hangup signal (SIGHUP), and so forth. Likewise, it must emulate
termios operations such as echo management and translate curses code
sequences into the appropriate X protocol commands.
These applications are known as terminal emulators. The granddaddy of them all is
xterm, which has been distributed with X11 since it was first released. Various terminal
emulators have been developed to extend or improve on xterm, including rxvt,
wterm, and eterm. Each of the major desktop environments also includes a terminal
emulator: GNOME has gnome-terminal and KDE has konsole.
Most of the Unix/Linux terminal emulators used with X understand the same codes
as the original xterm program, and therefore are usually used with the TERM environment
variable set to xterm (since the xterm codes are based on those used by the
DEC VT102 terminal, which were later standardized in ANSI X3.
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