Question

I have a CSV file that look like this:

A,B,C
1,2,3
4,4,4
1,2,6
3,6,9

Is there an easy way to grep all the rows in which the B column is 2, and keep the header? For example, I want the output be like

A,B,C
1,2,3
1,2,6

I am working under linux

Answer 1

Using awk:

awk -F, 'NR==1 || $2==2' file

NR==1 -> if first line,
$2==2 -> if second column is equal to 2. Lines are printed if either of the above is true.

To choose the column using the header column name:

awk -F, -v col="B" 'NR==1{for(i=1;i<=NF;i++)if($i==col)break;print;next}$i==2'  file

Replace B with the appropriate name of the column which you want to check against.