17   global obsFKey, geoFKey, diagFKey, fPrefixes
 
   18   parser.add_argument(
"-o", 
"--oPrefix", default = fPrefixes[obsFKey],
 
   19                       help=
"prefix for ObsSpace files")
 
   20   parser.add_argument(
"-g", 
"--gPrefix", default = fPrefixes[geoFKey],
 
   21                       help=
"prefix for GeoVaLs files")
 
   22   parser.add_argument(
"-d", 
"--dPrefix", default = fPrefixes[diagFKey],
 
   23                       help=
"prefix for ObsDiagnostics files")
 
   28     obsFKey:  args.oPrefix,
 
   29     geoFKey:  args.gPrefix,
 
   30     diagFKey: args.dPrefix,
 
def add_arguments(parser)