How to compare and sort 2 csv's to show difference

Question

Hi I have 2 csv\'s in the following format, (basically a list of email and the number of times we have been emailed by that sender):

file1.csv

Email,Val         


        

Answer 1

using join program

join -t, -o0,1.2,2.2 -a1 -a2 <(sort 

otherwise if files are already sorted and contain the same entries with bash builtins

while
    IFS=, read -u3 em1 val1
    IFS=, read -u4 em2 val2
    [[ -n $em1 ]] && [[ -n $em2 ]]
do
    if [[ $em1 = $em2 ]]; then
        echo "$em1,$val1,$val2"
    else
        echo "ERROR: $em1 <> $em2"
    fi
done 3