images,s,a,,,,Images to be operated upon
fields,s,a,,,,fields to be edited
value,s,a,.,,,value expression
comment,s,a,'.',,,Keyword comment
comfile,s,h,"",,,Command file
after,s,h,"",,,keyword name to insert after
before,s,h,"",,,keyword name to insert before
update,b,h,yes,,,Update image header?
add,b,h,no,,,add rather than edit fields
addonly,b,h,no,,,add only if field does not exist
delete,b,h,no,,,delete rather than edit fields
rename,b,h,no,,,rename field names
verify,b,h,yes,,,verify each edit operation
show,b,h,yes,,,print record of each edit operation