Embed Notice

@tinker

-F',' specifies the field separator as a comma

NR==FNR{a[$1]=$2; next} reads the first file (file2.csv) and stores its second field in an array a indexed by the first field

{print $0","a[$2]} reads the second file (file1.csv) and prints each line followed by the corresponding value in the a array indexed by the second field