Path: utzoo!attcan!uunet!paralogics!shaw
From: shaw@paralogics.UUCP (Guy Shaw)
Newsgroups: comp.unix.wizards
Subject: rsh does not pass back return code
Keywords: rsh, return code
Message-ID: <256@paralogics.UUCP>
Date: 5 Dec 89 19:48:12 GMT
Organization: Paralogics; Santa Monica, CA
Lines: 57

Rsh does not seem to pass back the return code from the command
executed on another machine.

I tried this little shell script:

  #! /bin/sh

  NEIGHBOR=<some other machine on the local network>

  rsh $NEIGHBOR /bin/false
  echo "'rsh $NEIGHBOR /bin/false' => $?"
  exit 0

It confirms my suspicion that no matter what happens on the remote machine,
rsh succeeds.  The only non-zero return codes that come from rsh are for
things that can go wrong before the remote command is executed, such as
invalid hostname.

It seems to be pretty common practice to do things like tape backups with
commands like:

  rsh tapeless /usr/etc/dump ... | dd of=/dev/localtape ...

and just hope that nothing goes wrong with the dump.  Ugh!

I often have the situation where a diskless workstation wants to do a grep
or a sort or some such command where at least the input and possibly both
input and output are files residing on a fileserver.  Especially in the case
of selection commands, it would be a lot cheaper to run the command on the
fileserver, rather than ship the program over via NFS, then read the entire
file via NFS, only to select out most of the lines.  I would do this using
rsh, except that rsh ignores error return codes.

Either some other method must be used to determine the success or failure
of work assigned to another machine, or I need to get a version of rsh or
something similar that passes back the remote machine's return code.

Before I spend time rolling my own reliable rsh equivalent, I would like to
know if this has already been done.  You need not bother telling me about
special arrangements made between clients and servers that know about each
other, such as client/server model database products; I am aware of their
existence and assume that they have solved the problem for themselves.
But, what about the good old Unix(TM)-philosophy tool-building approach?
You know, small general tools that do one job well, and all that.  Replies
to the effect that ignoring return codes is also part of the Unix philosophy
will be noted and filed in this big archive I have for information that may
contain some truth but but serves no constructive purpose.

I have RTFM, but I would be most happy if someone wants to tell me how dense
I am and point out the method that is already in there.

Thanks in advance
--
-- 
Guy Shaw
Paralogics
paralogics!shaw@uunet.uu.net  or  uunet!paralogics!shaw