i am recieving a flat file ( comma seperated ) with comma in between double quotes in any of the source fields . i need to remove the comma in double quotes and process the file thereafter

fields in file
=========
col1,col2,col3,col4

input can be any of the followng
=======================
rohan,rahul,kunal,"sw,ati"
rohan,rahul,"kun,al",swati
rohan,"rah,ul",kunal,swati
"ro,han",rahul,kunal,swati

the output should be
=============
rohan,rahul,kunal,swati

how can we achieve this ..
thanks in advance