#!/bin/bash

#Ensure that only one non-hyphened argument
function CompanyName
{
    for arg in $@
    do
        #Ignore arguments that begin with -
        if ! [[ ${arg:0:1} == "-" ]]
        then # argument does not begin with a hyphen
            if [[ $CompanyName ]]
            then
                1>&2 echo "Error:  Only one Comppany Name Permitted."
                exit 2
            fi
            CompanyName=$arg
        fi

    done

}

#Check if a variable is a valid positive integer
function numberp
{
    if [[ $# -ne 1 ]]
    then
        1>&2 echo "Error in argnum to numberp"
        exit 2
    fi

    re='^[0-9]+$'
    if [[ $1 =~ $re ]]
    then
        return 0
    else
        return 1
    fi
 }

#Add all number that follow a -a argument
function AddNumbers
{
    Total=0
    for arg in $@
    do
        if [[ ${arg:0:2} == "-a" ]]
        then
            value=${arg:2} #everything after the -a
            if numberp $value
            then
                Total=$(( $Total + $value ))
            else
                2>&1 echo "Error: $value is not a number"
                exit 3
            fi
        fi
    done
}

#Main Routine
CompanyName $@
AddNumbers $@
echo "$CompanyName owes me \$$Total!!"