after i executed sed, this is the output, and that is wrong:
this is a test,this is a test,this is a test,TEST,,,,,,,,,,,,,,,,,this is a test,,,,,this is a test,,,,,
it should look like this:
this is a test,this is a test,this is a test,,,,,,,,,,,,,,,,,,tTESThis is a test,,,,,this is a test,,,,,