For example if you are interested in comparing the differences between the data values of two GRIB files, you can blocklist (exclude) certain keys which show up in the comparison e.g.,
% grib_compare file1.grib1 file2.grib1
long [binaryScaleFactor]: [-4] != [-11]
double [referenceValue]: [-1.21940258789062500000e+03] != [-1.26698560714721679688e+01]
absolute diff. = 1206.73, relative diff. = 0.98961
tolerance=0.000244141
long [N]: [2694] != [1958]
long [P]: [1385] != [712]
double [values]: 4139 out of 4160 different
max absolute diff. = 9.1467330932617188e+01, relative diff. = 0.319192
max diff. element 0: 1.95091751098632812500e+02 2.86559082031250000000e+02
tolerance=0.0000000000000000e+00 packingError: [0.0313721] [0.000244617]
% grib_compare -bbinaryScaleFactor,referenceValue,N,P file1.grib1 file2.grib1
You can also include what you want to compare rather than exclude with a blocklist. E.g.
% grib_compare -c values file1.grib1 file2.grib1
Now only the values array is compared. Now you can use the -P, -R and -A flags to control the tolerances.