randy@umn-cs.cs.umn.edu (Randy Orrison) (04/14/88)
System: Silicon Graphics running SGI Unix 3.5 (?)
Silicon Graphics running ATT System V Release 3.2
I'm working on a project where we want to have a program talking to another
machine. I'd like to be able to have the program open up a couple pipes and
the fork off telnet to do the talking, but simple experiments with telnet
are proving to be dismal failures. I've tried the following approaches:
cat - | telnet
cat -u - | telnet
telnet < /dev/tty
The first two result in telnet accepting the "open" command and connecting,
but then ignoring the rest of my input, until I hit the intr key when telnet
acts as if it were processing my past input at the telnet> prompt. E.g.:
% cat - | telnet
telnet> open george
...connected...
Silicon Graphics (george)
(nothing.... i type: open george)
(nothing.... i hit DEL)
telnet> already connected to george telnet>
connection closed
%
(rough paraphrase). The last one (telnet < /dev/tty) hangs up the console
and requires a reboot.
On the vax running 4.3 here, the first two do about the same things, but the
last works just fine.
I suspect that telnet is doing some ioctls that screw up pipes. Does anyone
have any ideas what I can do? Note that I need the solution for System V
so i don't have ptys available (always did like BSD better...).
Thanks for all you help!
-randy
--
Randy Orrison, Control Data, Arden Hills, MN randy@ux.acss.umn.edu
(Anyone got a Unix I can borrow?) {ihnp4, seismo!rutgers, sun}!umn-cs!randy
What is a magician but a practising theorist?
-- Obi-Wan Kenobirandy@ncifcrf.gov (The Computer Grue) (04/17/88)
I'm pretty sure that the problem here is that when telnet does the
open it puts the terminal into raw mode and simply transfers
characters to the remote system. This means that you need to send
<CR> to end lines instead of <LF>, which is the normal unix end of
line character. This explains everything you described except the
console hanging on the tty indirect, but then I always knew SGI had
flaky OS software! I had this same problem attempting to get telnet
working on input from a regular disk file.
Try translating <LF> to <CR> on the cat (does tr buffer? If so,
you'll have to write a C program to do it); that should fix your
problem. Hope this helps . . .
-- Randy
--
Randy Smith @ NCI Supercomputer Facility
c/o PRI, Inc. Phone: (301) 698-5660
PO Box B, Bldng. 430 Uucp: ...!uunet!ncifcrf.gov!randy
Frederick, MD 21701 Arpa: randy@ncifcrf.govbarnett@vdsvax.steinmetz.ge.com (Bruce G. Barnett) (04/18/88)
In article <443@ncifcrf.ncifcrf.gov> randy@ncifcrf.gov (The Computer Grue) writes: [ telnet with a script] |This means that you need to send |<CR> to end lines instead of <LF>, which is the normal unix end of |line character. Don't forget the Login: and Password: lines. These are not terminated by <CR> or <LF>. I hacked together a simple program for a remote telnet script. (Our Internet gateway doesn't do IP forwarding and isn't BSD based.) I am not satified I did it the most efficient way. I forked a telnet process and connected to it using pipes. I then used fcntl to add the FNDELAY flag. I experimented with different values to distinguish from a timeout and a line without a <cr><lf>. I wrote my own buffering scheme. Anyhow, the program works - more-or-less, but I can't help wondering is there is a better way. Anyone have any suggestions? I plan to study the sources of telnet and rlogin - for inspiration. Sigh ... it is amazing how a simple 2-hour hack grows in size to fill all available time. -- Bruce G. Barnett <barnett@ge-crd.ARPA> <barnett@steinmetz.UUCP> uunet!steinmetz!barnett