I thought the V6 Mashey shell didn't have anything built in, but there were external commands such as goto that would seek the open file descriptor to a location matching a label, which would be a comment (beginning with a colon, which was a no-op command.)  There would also have been an "if" command or option to goto or something.

On 07/14/2016 06:23 AM, Clem Cole wrote:
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@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.)