Shell Programming and Scripting

read input

while [ $input < 9999 ] 
do
           while [ 'echo $input | wc -c' < 4 ]
           do
                      while [ "$input" = 'grep $input file' ] 
                      do
                      read input
                      done
           read input
           done
read input
done

while true
do
  echo "Enter you number"
  read input
  if [ $input -lt 9999 -a ${#input} -eq 4 -a "$input" != `grep $input $file` ]
  then
    break
  else
    echo "number doesnt meet requirements... these are the requirements: blah"
  fi
done

while read input; do
  if (( input > 999 && input < 10000  )) &&\
     [[ $(grep -c "$input" file) -eq 0 ]]; then
    break
  fi
done

while read input; do
  case $input in
    [0-9][0-9][0-9][0-9])
      if [[ $(grep -c "$input" file) -eq 0 ]]; then
        break
      fi
  esac
done

while read input; do
  case $input in
    [0-9][0-9][0-9][0-9])
      grep "$input" file >/dev/null || break ;;
  esac
done