Read in and parse the input file

For example the input file is world_cties.txt

ad,Andorra La Vella,07,20430,42.5,1.5166667 ad,Canillo,02,3292,42.5666667,1.6 ad,Encamp,03,11224,42.5333333,1.5833333 ad,La Massana,04,7211,42.55,1.5166667 ad,Les Escaldes,08,15854,42.5,1.5333333 ad,Ordino,05,2553,42.55,1.5333333 ad,Sant Julia De Loria,06,8020,42.4666667,1.5 ae,Abu Dhabi,01,603687,24.4666667,54.3666667 ae,Dubai,03,1137376,25.2522222,55.28 ae,Sharjah,06,543942,25.3622222,55.3911111 af,Acin,18,15098,34.081667,70.668333 af,Anar Darreh,06,10023,32.762222,61.6525 af,Andarab,03,27034,35.634444,69.259444 af,Asadabad,34,48400,34.8725,71.146111 af,Asmar,34,15708,35.033056,71.357778 af,Aybak,32,47877,36.265278,68.016667 af,Azrow,36,12526,34.173333,69.645278 af,Baglan,03,108481,36.126944,68.705278 af,Bagrami,13,30256,34.494167,69.274722 af,Baraki Barak,17,22305,33.9675,68.948611 af,Cah Ab,26,23424,37.399444,69.815278 af,Carikar,22,53693,35.013611,69.171389 a

the output file citypopulation.txt

Andorra La Vella,07,20430,42.5,1.5166667 Canillo,02,3292,42.5666667,1.6 Encamp,03,11224,42.5333333,1.5833333 La Massana,04,7211,42.55,1.5166667 Les Escaldes,08,15854,42.5,1.5333333 Ordino,05,2553,42.55,1.5333333 Sant Julia De Loria,06,8020,42.4666667,1.5 Abu Dhabi,01,603687,24.4666667,54.3666667 Dubai,03,1137376,25.2522222,55.28 Sharjah,06,543942,25.3622222,55.3911111 Acin,18,15098,34.081667,70.668333 Anar Darreh,06,10023,32.762222,61.6525 Andarab,03,27034,35.634444,69.259444 Asadabad,34,48400,34.8725,71.146111 Asmar,34,15708,35.033056,71.357778 Aybak,32,47877,36.265278,68.016667 Azrow,36,12526,34.173333,69.645278 Baglan,03,108481,36.126944,68.705278 Bagrami,13,30256,34.494167,69.274722 Baraki Barak,17,22305,33.9675,68.948611 Cah Ab,26,23424,37.399444,69.815278 Carikar,22,53693,35.013611,69.171389

Please do it using c programing