Shell Programming and Scripting

HOSTLIST="test1 test2 test3"

List_Hosts ()
{
  num=1
  hosts=
  HI_HOSTS=
  hostlist=(NULL $( echo $HOSTLIST ))
  hostnumbers=${#hostlist[@]}
  for (( i=1; i<${hostnumbers}; i++ )); do
    hosts=$( echo "$hosts($num)-${hostlist[$i]} " )
    let num=num+1
  done
  echo -e "\n$hosts\n"
  echo -n "Enter number(s) (comma-separated - 1,2,3): "
  read input
  if [ -n "$( echo "$input" | tr , " " | tr -d '[0-9]' | awk '{print $1}' )" ]; then
    echo -e "\nNone numerical value \"$input\" entered, please try again."
    List_Hosts
  else
    for hostnum in $( echo "$input" | tr , " " ) ; do
      if [ "$hostnum" -eq 0 -o "$hostnum" -gt $[$hostnumbers-1] ]; then
        echo "Number \"$hostnum\" doesn't match existing values, please try again."
        List_Hosts
      fi
      HI_HOSTS=$( echo "$HI_HOSTS${hostlist[$hostnum]} " )
    done
  fi
}
List_Hosts
echo $HI_HOSTS

     HI_HOSTS=$( echo "$HI_HOSTS${hostlist[$hostnum]} " )

    for hostnum in $( echo "$input" | tr , " " ) ; do
      if [ "$hostnum" -eq 0 -o "$hostnum" -gt $[$hostnumbers-1] ]; then
        echo "Number \"$hostnum\" doesn't match existing values, please try again."
        List_Hosts
      fi
    done
    for hostnum in $( echo "$input" | tr , " " ) ; do
      HI_HOSTS=$( echo "$HI_HOSTS${hostlist[$hostnum]} " )
    done

# pseudo code
valid-input=false
while ! valid-input
  prompt
  get input
  for each hostnum
     if hostnum is invalid
        invalid-hosnum=TRUE
        echo "hostnum doesn't match"
     else
        hosts=$hosts + $hostlist[ hostnum ]
   if invalid-hostnum 
      echo Please try again
   else
      valid-input=TRUE
return $hosts