If fields names are included in CSV input data, the set of field names are usually included in the output corresponding to the context of data processing.
On the other hand, if the CSV input data do not include field names, and data is 0 byte file, the result will also return 0 byte file. Both the number of input and output records are 0.
$ more dat1.csv A,B,C $ msetstr v="string" a=X i=dat1.csv o=rsl1.csv #END# kgsetstr a=X i=dat1.csv o=rsl1.csv v=string $ more rsl1.csv A,B,C,X
$ more dat2.csv $ msetstr v="string" -nfn i=dat2.csv o=rsl2.csv #END# kgsetstr -nfn i=dat2.csv o=rsl2.csv v=string $ more rsl2.csv