Tornado

5
Shell
Figure 5-3
Components of the Tornado Shell
Developer
Commands
Line Editing and History
5
TORNADO
SHELL
C
Interpreter
Tcl
Interpreter
WTX Tcl Back End
Target
Server
WTX Tcl
The back-end mechanism that ties together all of Tornado; the Wind River
Systems Tool Exchange protocol, implemented as a set of Tcl extensions.
5.8.3 Layers of Interpretation
In daily use, the shell seems to be a seamless environment; but in fact, the
characters you type in WindSh go through several layers of interpretation, as
illustrated by Figure 5-4. First, input is examined for special editing keystrokes
(described in 5.5 Shell Line Editing, p.193). Then as much interpretation as possible
is done in WindSh itself. In particular, execution of any subroutine is first
attempted in the shell itself; if a shell built-in (also called a primitive) with that
name exists, the built-in runs without any further checking. Only when a
subroutine call does not match any shell built-ins does WindSh call a target
routine. See 5.2.3 Invoking Built-In Shell Routines, p.156 for more information. For a
list of all WindSh primitives, see Table 5-13. .
205