The -if_n option is an -if for a range of inventory numbers.
The -if_n option uses the same syntax as the "for_n" option.
If you want to operate on
inventory records 10 to 20, you would use the parameter 10:20.
If you want to operate on all the even inventory records from 10 to 20, you would
use 10:20:2. The restrictions are the start value must be less than
the ending value and the step has to be greater than zero.
The -if_n option is similar to the
-for_n option in that they both select a range of invetory records.
The difference is that the -for_n option selects the range
of records that wgrib2 will process. With the
the -if_n option, all the records will be processed
but only the additional processing within the -if block will be only
done for the selected records. The -for_n option can be much
faster if the field has to be decoded. With the -for_n option,
only the selected records need to be docoded whereas all the records would be decoded
when using the -if_n option. The command line, however,
can have multiple -if_n options.
-if_n I:J:K same as for n = I to J by K
-if_n I:J same as for n = I to J by 1
-if_n I::K same as for n = I to MAX_INTEGER by K
-if_n I same as for n = I to MAX_INTEGER by 1
$ wgrib2 file.grb2 -if_n 4:5 -s -fi
5:17098:d=2008120200:TMP:2743 m above mean sea level:anl:
See also: -match