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20010525: rsh and ssh within mcenv subshells

>From: Jim Nelson <address@hidden>
>Organization: SSEC
>Keywords: 200105242058.f4OKw9p09179 McIDAS-X shell scripts mcenv ssh rsh

------- Forwarded Message

Date: Thu, 24 May 2001 15:56:05 -0500
To: tim Schmit <address@hidden>, address@hidden,
   address@hidden, geary callan <address@hidden>,
   joleen feltz <address@hidden>, address@hidden,
   fred wu <address@hidden>, jun li <address@hidden>,
   tony schreiner <address@hidden>, address@hidden,
From: Jim Nelson <address@hidden>
Subject: rsh and ssh within mcenv subshells

Hey all--  Just wanted to pass something along that might affect you if you
use either the rsh or ssh commands within the McIDAS-X mcenv

Assume we have something like the following:

mcenv << 'EOF'

   ssh command
   echo "We are here now..."


We were encountering a situation where an ssh command embedded
within a mcenv session was causing a premature exit from the mcenv.  In other
words, we would never see the "We are here now..." echo to our screen.

As it turns out, ssh receives information from the remote host via stdin,
and this information then overwrites the remainder of the mcenv session that
has already been read into stdin via the << construct.

THE FIX:   Use the -n flag with either the rsh or ssh commands, to suppress
                 input from stdin.  This then maintains the integrity of 
your mcenv
                 session, and everything works as planned...


Sincerely,  Jim Nelson

------- End of Forwarded Message

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