[net.sources] csh and shell layers request/question

sgt@alice.UucP (Steve Tell) (04/30/86)

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

gwyn@brl-smoke.ARPA (Doug Gwyn ) (05/03/86)

In article <5366@alice.uUCp> sgt@alice.UucP (Steve Tell) writes:
>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).

There is a program called "mpx" in use for Teletype 5620 DMDs.
It does more than is needed for simple "shl" emulation, however,
since it operates in parallel with an operating system in the
5620, using suitable packet and control protocols.  Once could
take the existing "mpx" source and remove a lot of 5620-specific
stuff from it to obtain an "shl"-like multiplexer.  I don't know
anyone who has done that; what would be the point of it when you
have Berkeley-style ^Z job control available for dumb terminals?