Shell Programming and Scripting

#!/bin/bash
# Make sure you have the correct hostname set on Servers, If you have the incorrect hostname it will get updated in conf"
hostsfile=/home/userid/hostname/servers.txt

if [[ ! -r $hostsfile ]]; then
    echo "ERROR: Cannot read hostsfile $hostsfile"
    exit 2
fi

SSH_OPTS="-q -i /home/userid/userid.pem -o PasswordAuthentication=no -o BatchMode=yes -o StrictHostKeyChecking=no -o ConnectTimeout=3"

for destination in `cat $hostsfile`; do
shortname=`echo $destination | sed 's/.sys.domain.com//g'`
echo $shortname
export shortname
ssh -tt -i $SSH_OPTS xxx@$destination '
echo "INFO: Updating /etc/sysconfig/network"
sudo perl -pi -e "s/^HOSTNAME=\"\"/HOSTNAME=\"$shortname\"/g" /etc/sysconfig/network
sudo hostname $shortname
'
done

var=value; ssh -o SetEnv=var user@host 'var_here=var; echo $var_here'

while read line
do
    do_something_with $line
done < /path/to/file