14 Jul
2016
14 Jul
'16
7:23 p.m.
Could you be confusing the fact the true and false were implemented by
external commands in some early shell's
On Thu, Jul 14, 2016 at 9:18 AM, Diomidis Spinellis <dds(a)aueb.gr> wrote:
I remember hearing that originally the Unix shell had
control structures
(e.g. if, while, case) implemented through external commands. However, I
can't see this reflected in the source code. The 7th Edition Bourne shell
has these commands built-in (usr/src/cmd/sh/cmd.c), while the 6th Edition
(usr/source/s2/sh.c) seems to lack them completely.
The only external command I found was glob, which performed wildcard
expansion.
Am I missing something? Was this implemented in a version that was never
released? If so, does anyone know how this implementation worked? (Nested
commands might require holding some sort of globally accessible stack.)