[TUHS] Shell control through external commands
Mary Ann Horton
mah at mhorton.net
Fri Jul 15 00:12:57 AEST 2016
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 at aueb.gr
> <mailto: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.)
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the TUHS