Group rows of a csv file with sum of column values

You have heard about Group functionality in Microsoft Excel, which group the rows on a common value and does the sum of other field. Same thing can be done in unix using awk very easily. See below example:

[ ~]# cat test.csv
a,5
b,10
a,4
c,8
b,9
b,4
[ ~]# awk -F"," '{sum[$1] += $2 } END { for(n in sum)print n"=" sum[n] }' test.csv
a=9
b=23
c=8

Perl version of above script can be seen here: