The sum command produces a numeric total of a given attribute for all items meeting the optional selection criteria. If an attribute name (attribute name or number) is not specified, the total number of characters in the selected items are calculated. If only the file reference is specified, the total number of characters in the entire file is calculated, including attribute and value marks.
sum file.reference {item.list} attr.name{selection.criteria} {(options)}
sum invoices amount (p