Design and Implementation of a Documentation Tool for ... - MADOC

• Converting a forscript file to a script file is basically as easy as removing
everything between shift out and shift in bytes (while respecting
escaping rules, of course).
4 Implementation Oveview
We give a brief insight into the code of forscript that is assembled within a
single C source file and written as a literate program [4] using the tool noweb [5].
The noweb tool automatically introduces cross-references between code chunks
so that readers can quickly find the corresponsing code. We only show the most
interesting code chunks here. The full details can be found in the appendix.
7a 〈forscript.c 7a〉≡
〈declarations and definitions 15b〉
〈functions 15c〉
〈main 7b〉
4.1 The Main Program
Here is the main() function. We first determine the program’s name (as called
on the command line), then we process the command line options. Afterwards
we open the output file and a new pseudo terminal. The original script uses
one process to listen for input, one to listen for output and one to initialize
and execl() the command to be recorded. forscript in contrast uses only
the select() function to be notified of pending input and output and therefore
only needs two processes: itself and the subcommand. These two processes
are forked after registering the appropriate signal handlers. Since neither the
parent nor the child process should ever reach the end of main(), it returns
EXIT FAILURE.
7b 〈main 7b〉≡ (7a)
int main(int argc, char *argv[]) {
〈set my name 24c〉
〈process command line options 25b〉
〈open output file 26c〉
〈open new pseudo terminal 28e〉
〈register signal handlers 8a〉
〈fork subprocesses 8c〉
return EXIT_FAILURE;
}
Defines:
main, never used.
4.2 Registering Signal Handlers
To be notified of an exiting subprocess, a handler for the SIGCHLD signal needs
to be defined. This signal is usually sent by the operating system if any child
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