Indicate the field number with "F=x" where x is a number. The fields are determined by the second parameter. If, for example, you pass "," as parameter 2, a field would correspond to an item. If you were to pass a space as parameter 2, a field would correspond to a word.
Any character can be used as a field delimiter. If you do not indicate a field, the entire record will be used as the key.
Indicate the sort direction with "D=x" where x is "A" or "D", for ascending or descending, respectively. If you do not indicate the sort direction, the default is ascending.