[ILUG] user change during script execution

[Richard O'Mahony]

Hi,
	I am working on a bash script in which I have to change user during the
processing of the script in order to check certain environment variables are
being correctly set for that user. Currently I am using the following
appraoch

change_user () {
    NEW_USER=$1
    echo "logging in as $NEW_USER."
    su - $NEW_USER

  #
  #plus some error checking
  #to ensure that the log in proceeds
  #
}


change_user ismadm
#
#some commands to be run as ismadm user
#

the problem is that when I log in using the above approach is that the
script seems to be halted and the terminal presents a log in for the
$NEW_USER. I am looking for some method to login and run a few commands
without the user ever knowing (apart from supplying the password).
Thanks
Richard...