CentOS - Feb 2012 - Bash scripting - Remotely ran commands break while loop

I have two CentOS5 systems server1 and server2. There is user peter on
server1 who can ssh to server2 using public ssh keys and no password is
needed.

What I noticed is that running remote ssh commands in bash script breaks
while loops.

=====#!/bin/sh
for i in server2 server2; do
     echo "--> Start"
     ssh peter@$i ls
     echo "--> END"
done

echo " server2
server2" | \
while read confLine; do
     echo "--> $confLine"
     ssh peter@$confLine ls
     echo "--> END $confLine"
done
===
The "for" loop in the script above will run twice but the
"while" loop
below it will run only once.

This is very simple to test and I've tried it on different systems
including CentOS6 and OpenSolaris with the same result.

Any idea what would cause the ssh command to break the while loop?

Thanks
Peter

Am 01.02.2012 22:07, schrieb Peter Blajev:
> I have two CentOS5 systems server1 and server2. There is user peter on
> server1 who can ssh to server2 using public ssh keys and no password is
> needed.
> 
> What I noticed is that running remote ssh commands in bash script breaks
> while loops.
> 
> =====> #!/bin/sh
> for i in server2 server2; do
>      echo "--> Start"
>      ssh peter@$i ls
>      echo "--> END"
> done
> 
> echo " server2
> server2" | \
> while read confLine; do
>      echo "--> $confLine"
>      ssh peter@$confLine ls
>      echo "--> END $confLine"
> done
> ===> 
> The "for" loop in the script above will run twice but the
"while" loop
> below it will run only once.
> 
> This is very simple to test and I've tried it on different systems
> including CentOS6 and OpenSolaris with the same result.
> 
> Any idea what would cause the ssh command to break the while loop?
> 
> Thanks
> Peter
That has simply nothing to do with SSH. Compare following:

echo "foo bar" | while read LINE; do echo $LINE; done

and

echo -e "foo\nbar" | while read $LINE; do echo $LINE; done

Alexander

On Wed, Feb 01, 2012 at 01:07:31PM -0800, Peter Blajev
wrote:
> echo " server2
> server2" | \
> while read confLine; do
>      echo "--> $confLine"
>      ssh peter@$confLine ls
>      echo "--> END $confLine"
> done
> The "for" loop in the script above will run twice but the
"while" loop
> below it will run only once.
> Any idea what would cause the ssh command to break the while loop?
"ssh" is reading from stdin and passing the data over to the remote
machine.  You can test this with
  ssh peter@$confLine 'read x ; echo we got $x'

To stop it doing this, use the "-n" flag
  ssh -n peter@$confLine ls

-- 

rgds
Stephen