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

Pretty straight-forward with Awk!

awk 'BEGIN{FS=OFS=","; printf "Name,Value1,Value2\n"}NR >1 && FNR==NR{map[$1]=$2; next}$1 in map{$(NF+1)=map[$1]; print}' file2 file1

produces

Name,Value1,Value2
email1@email.com,2,3
email2@email.com,4,6
email3@email.com,1,8
email4@email.com,6,2

Set input and output field-separator to , in the BEGIN clause that gets executed before the input lines are processed and also the final header information needed. The part FNR==NR is run for the first file in order file2 in this case, create a hash-map, with an index set to the $1 and value set to $2 then on file1 for those lines whose hashed index value belongs in $1 create a new field $(NF+1) meaning the last field + 1 to the new value and print the result formed.

Answer 2

if you want to keep the order

awk to the rescue!

$ awk  'BEGIN   {FS=OFS=","}
        NR==FNR {a[$1]=$2; next} 
        FNR==1  {print $1,$2"1",a[$1]"2"; next} 
                {print $1,$2,a[$1]}' file2 file1

Email,Value1,Value2
email1@email.com,2,3
email2@email.com,4,6
email3@email.com,1,8
email4@email.com,6,2

note the order of files...

Answer 3

1. build a loop running through each line from the first file.

2. in that loop, build another loop comparing each line of the second file to the current line of the first file.

3. write matches to your new file.

Answer 4

using join program

join -t, -o0,1.2,2.2 -a1 -a2 <(sort <file1.csv) <(sort <file2.csv)

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<file1.csv 4<file2.csv