[Coco] Major OS-9 discovery to enhance script file use.

[Robert Gault]

You have found something there. I just ran procs before and after using 
a ()</1 command and two extra shells were generated.

tim lindner wrote:

> Robert Gault <robert.gault at worldnet.att.net> wrote:
> 
> 
>>(chd /h0/MVUE)</1
> 
> 
> I tested something like this on stock OS9 Level 2. I modified the
> startup file to have this at the end:
> 
> (chd sys) </1
> echo Success!
> 
> After it was done I got my prompt and did a PWD, and found my current
> directory really was /DD/SYS. But the echo command did not execute.
> 
> When shell runs the startup file (or any script) it forks a sub shell,
> changing directories in that sub-shell will not effect the parent shell.
> Period.
> 
> What you have found is a way to crash the sub shell, and exeucte the CHD
> command in the parent shells process. I think it crashes becuase you are
> trying to redirect the STDIN of a built in shell command.
> 
> 
>>(display 1b 21)</1
> 
>  
> This works becuase you dup STDOUT and assign it to STDIN. This works
> around a bug in Select when STDIN is an RBF path. Note, this does not
> crash the sub-shell.
>