csh and shell layers request/question

[Steve Tell]

As I understand it from the manual page and looking at the source code,
shl handles the multiplexing, and exec's a shell for each layer.
I don't recall if it looks at the password file or the SHELL
enviroment variable to decide if it should run sh, csh, ksh,
or whatever.
If not, there's no reason why you couldn't run csh on top of the
sh it runs for you.
If you're switching to SYS-V from a recent BSD, you'll miss the job
conrtol from csh & ksh.  Shl is all you get under SVR2.

BTW, has anyone written somthing like shl for BSD systems (using
pty's) or Version-8 (using pt's & line disciplines, etc)?
It shouldn't be too difficult with these features available.
Shl goes to lots of trouble, there's a special SYS-V device
driver that does the multiplexing. (called an sxt).

Steve Tell