[comp.unix.questions] login shell suspend

rjshaw@ramius.llnl.gov (08/15/90)

Hi.

Who knows the history behind "Can't suspend a login shell (yet)."

Is there a day when we will be able to do so, or is the "yet" a joke
that I don't understand? When I rlogin somewhere and <RET> ~ CNTL-Z <RET>
isn't that a suspension of the login shell on the remote machine? Isn't
suspension just sleeping?

No, I haven't read either of the internals books yet, but I'm planning
to get to the Berkeley one any day now [ half :-)  half :-( ]

Thanx in advance for responses

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                                                       rjshaw@ramius.llnl.gov
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brnstnd@kramden.acf.nyu.edu (Dan Bernstein) (08/19/90)

In article <498@llnl.LLNL.GOV> rjshaw@ramius.llnl.gov () writes:
> Who knows the history behind "Can't suspend a login shell (yet)."

When you suspend a shell, you're dumped back into the shell above it.
The ``logical'' extension of this behavior to a network is what rlogin
does when you type ~^Z at the beginning of a line. The connection is
still there, but rlogin ignores it.

The intuitive---and much more useful---extension of this behavior is
what my pty program does upon a typed or accidental disconnect. The
connection disappears entirely, but the tty session sticks around,
blissfully unaware of anything going on. Later you can reconnect, from a
different terminal, a different network, even piping input and output
through other programs. You don't get screwed by a dying terminal or a
fuzzy connection: just hang up, move to the next terminal, and
reconnect.

pty has only been widely available this summer; the shell is much older.
Whoever stuck ``Can't suspend a login shell (yet)'' into the shell was
dreaming of features only available in dreams, Steve Bellovin's proposed
session manager, and VMS. Now those features are here, for BSD at least.

---Dan