DESCRIPTION
Compare grib messages contained in two files. If some differences are found it fails returning an error code. Floating point values are compared exactly by default, different tolerance can be defined see -P -A -R. Default behaviour: absolute error=0, bit-by-bit compare, same order in files.
USAGE
grib_compare [options] grib_file grib_file
OPTIONS
-r
Compare files in which the messages are not in the same order. This option is time expensive.
-b key,key,...
All the keys in this list are skipped in the comparison. Bit-by-bit compare on.
-e
Edition independent compare. It is used to compare grib edition 1 and 2.
-c key[:i/d/s/n],key[:i/d/s/n],...
Only the listed keys or namespaces (:n) are compared. The optional letter after the colon is used to force the type in the comparison: i->integer, d->float, s->string, n->namespace. See -a option. Incompatible with -H option.
-S start
First field to be processed.
-E end
Last field to be processed.
-a
-c option modifier. The keys listed with the option -c will be added to the list of keys compared without -c.
-H
Compare only message headers. Bit-by-bit compare on. Incompatible with -c option.
-R key1=relative_error1,key2=relative_error2,...
Compare floating point values using the relative error as tolerance. key1=relative_error will compare key1 using relative_error1. all=relative_error will compare all the floating point keys using relative_error. Default all=0.
-A absolute error
Compare floating point values using the absolute error as tolerance. Default is absolute error=0
-P
Compare data values using the packing error as tolerance.
-T factor
Compare data values using factor multiplied by the tolerance specified in options -P -R -A.
-w key[:{s/d/i}]{=/!=}value,key[:{s/d/i}]{=/!=}value,...
Where clause. Messages are processed only if they match all the key/value constraints. A valid constraint is of type key=value or key!=value. For each key a string (key:s), a double (key:d) or an integer (key:i) type can be specified. Default type is string.
-f
Force. Force the execution not to fail on error.
-V
Version.
-7
Does not fail when the message has wrong length
-v
Verbose.
grib_compare examples
The default behaviour for grib_compare without any option is to perform a bit by bit comparison of the two messages. If the messages are found to be bitwise different then grib_compare switches to a "key based" mode to find out which coded keys are different. To see how grib_compare works we first set the shortName=2d (2 metre dew point temperature) in the file regular_latlon_surface.grib1
Code Block > grib_set -s shortName=2d regular_latlon_surface.grib1 2d.grib1