Check to see if a User exists. If so break with the check on move on.

check-user-exist.sh

#!/bin/bash

COUNTER=0
USER='blah'

while [  $COUNTER -lt 10 ]; do
  if [ `id -u $USER 2>/dev/null || echo -1` -ge 0 ]; then
    echo 'User Found... Moving on...'
    break
  else
    echo 'User Not Found... Retrying...'
    sleep 2 
  fi
    let COUNTER=COUNTER+1
done