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

If datamash is okay

$ datamash -t' ' -g 1 sum 2 < ip.txt 
1486113768 9936
1486113769 6160736
1486113770 5122176
1486113772 4096832
1486113773 9229920
1486113774 8568888

• -t' ' set space as field delimiter
• -g 1 group by 1st field
• sum 2 sum 2nd field values
• if the input file is not sorted, use datamash -st' ' -g 1 sum 2 where the -s option takes care of sorting