[TUHS] Shell control through external commands

Clem Cole clemc at ccc.com
Thu Jul 14 23:23:04 AEST 2016

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 at 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.)
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