use variable refeences in awk

I need to compare 1st column of user.csv with value, it works well with following

value=2
awk -F':' '$1==$value {print}' user.csv

now I have a case where column number is also a variable for me, in that case, the solution would be:

value=2
column=1
awk -F':' ''\$$column==$value' {print}' filename

1. You need to put backslash (\) before first $
2. You need to put comparison in single quote

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:

AWK examples

Find number of columns in a pipe seperated csv file
awk -F"|" '{print NF}' vishnu.csv |uniq

Find sum of column of a pipe seperated csv file
awk -F"|" '{sum += $col } END { print sum }' vishnu.csv
awk -F"|" '{sum += $col } END { print sprintf("%.2f",sum) }' vishnu.csv (print float value)

Replace tab character with a pipe symbol in a csv file
awk '{gsub("\t","|");print}' vishnu.csv

print the 5th and 7th columns of csv file if 5th and 7th column values are not same
awk -F"," '{if($5 != $7) {print $5","$7}}' test.csv

print the line of csv file if 5th and 7th column values are same
awk -F"," '{if($5 !== $7) {print}}' test.csv