12 Sep
2014
12 Sep
'14
7:54 a.m.
From: Dave Horsfall <dave(a)horsfall.org>
On the *nix systems to which I have access, bc(1) is a
standalone
program on FreeBSD and OSX, but pipes to dc(1) on OpenBSD. I cannot
check my Penguin box (Ubuntu)
Dude! Trying to answer questions about the origins of BC by looking at
systems this late is like trying to learn Latin by studying Italian! :-)
I looked at the Version 6 source, and it's a bunch of YACC code, but it pulls
the same technique of using a pipe to an instance of DC, viz:
pipe(p);
if (fork()==0) {
close(1);
dup(p[1]);
close(p[0]);
close(p[1]);
yyinit(argc, argv);
yyparse();
exit();
}
close(0);
dup(p[0]);
close(p[0]);
close(p[1]);
execl("/bin/dc", "dc", "-", 0);
There's likely even older versions than the V6 one, but that's the earliest
source I have online on my PC for easy access.
Noel