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Where clause. Set is only executed for grib messages matching all the key/value constraints. If a grib message does not match the constraints it is copied unchanged to the output_grib_file. This behaviour can be changed setting the option -S. 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 defined. Default type is string. In the value you can also use the forward-slash character '/' to specify an OR condition (i.e. a logical disjunction) Note: only one -w clause is allowed.
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To set productDefinitionTemplateNumber=2 only for the fields with productDefinitionTemplateNumber=11
Code Block > grib_set -s productDefinitionTemplateNumber=2 -w productDefinitionTemplateNumber=11 ../data/tigge_pf_ecmwf.grib2 out.grib2
To set productDefinitionTemplateNumber=2 only for the fields for which productDefinitionTemplateNumber is not equal to 11
Code Block > grib_set -s productDefinitionTemplateNumber=2 -w productDefinitionTemplateNumber!=11 tigge_pf_ecmwf.grib2 out.grib2
When a key is not used all the bits of its value should be set to 1 to indicate that it is missing. Since the length (number of octet) is different from a key to another, the value that we have to code for missing keys is not unique. To give an easy way to set a key to missing a string "missing" or "MISSING" is accepted by grib_set as follows:
Since some values can not be set to missing you can get an error for those keys.Code Block > grib_set -s scaleFactorOfFirstFixedSurface=missing,scaledValueOfFirstFixedSurface=MISSING ../data/regular_latlon_surface.grib2 out.grib2
To set scaleFactorOfSecondFixedSurface to missing only for the fields for which scaleFactorOfSecondFixedSurface is not missing:
Code Block > grib_set -s scaleFactorOfSecondFixedSurface=missing -w scaleFactorOfSecondFixedSurface!=missing tigge_pf_ecmwf.grib2 out.grib2
It's possible to produce a grib edition 2 file from a grib edition 1 just changing the edition number with grib_set. At this stage of development all the geography parameters, level and time information is correctly translated, for the product definition extra set calls must be done. To do this properly, \ref please use the grib_filter is suggestedtool.
Code Block grib_set -s edition=2 ../data/reduced_gaussian_pressure_level.grib1 out.grib2
With grib edition 2 is possible to compress data using the jpeg algorithm. To change packing algorithm from grid_simple (simple packing) to grid_jpeg (jpeg2000 packing):
Code Block > grib_set -s packingType=grid_jpeg ../data/regular_gaussian_model_level.grib2 out.grib2
It's possible to ask ecCodes to calculate the number of bits per value needed to pack a given field with a fixed number of decimal digits of precision. For example if we want to pack a temperature expressed in Kelvin with 1 digits of precision after the decimal point we can set changeDecimalPrecision=1
Code Block > grib_set -s changeDecimalPrecision=1 ../data/regular_latlon_surface.grib2 ../data/out.grib2