This article relates to GRIB edition 2
Step-by-step guide
To convert multi-field GRIB messages into single-field, you can use the grib_copy command. For example:
% grib_copy multi.grib2 single.grib2 % grib_count multi.grib2 30 % grib_count single.grib2 56
The use of the multi-field feature is not recommended.