[TUHS] Shell control through external commands

Dan Cross crossd at gmail.com
Mon Sep 12 04:27:48 AEST 2016

On Sun, Sep 11, 2016 at 1:39 PM, Doug McIlroy <doug at cs.dartmouth.edu> wrote:

> > IIRC #! originated at Bell Labs but it got out to the world via BSD.
> > Perhaps Dr. McIlroy could confirm / deny / expand upon the details
> (please?)
> I recall Dennis discussing the feature at some length before installing it.
> So the exact semantics, especially the injected argument, are almost]
> certainly his. I don't know whether he built on a model from elsewhere.
> #! appeared between v7 (1979) and v8 (1985). As v8 was never released,
> it clearly made its way into the world via BSD and USG. BSD, being
> more nimble, was likely first.

Also, 8th edition was essentially a re-port of 4.1c BSD, correct? If it
were already in BSD, it could conceivably come back into 8th edition via
that route. I found the following in /usr/src/sys/sys/TODO for 4.0BSD:

6. Exec fixes
>         Implement dmr's #! feature; pass string arguments through faster.

That would strongly imply that the feature originated with Dennis and was
known in Berkeley around the time for 4BSD.

4.0's 'getxfile()' in /usr/src/sys/sys/sys1.c does not recognize the '#!'
sequence as a magic number, but 'exece()' in /usr/src/sys/newsys/sys1.c
does. No mention of it came up in my cursory scan of 3bsd. So it was
certain present by the time of 4.1c, but not before 4BSD that I found.

        - Dan C.
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