Sum duplicate row values with awk

Question

I have a file with the following structure:

1486113768 3656
1486113768 6280
1486113769 530912
1486113769 5629824
1486113770 5122176
1486113772 3565920
148611         


        

Answer 1

Use an Awk as below,

awk '{ seen[$1] += $2 } END { for (i in seen) print i, seen[i] }' file1
1486113768 9936
1486113769 6160736
1486113770 5122176
1486113772 4096832
1486113773 9229920
1486113774 8568888

{seen[$1]+=$2} creates a hash-map with the $1 being treated as the index value and the sum is incremented only for those unique items from $1 in the file.