How do I copy a selected number of messages from a GRIB file? - ecCodes GRIB FAQ

How do I copy a selected number of messages from a GRIB file?

Step-by-step guide

Say you want to copy the first 3 messages. This can be done with:

% grib_copy -w count=1/2/3 in.grib out.grib

1. But it is better to write a rules file and use grib_filter:

   my.filter

   if (count < 4) {
     print "Copying message number [count]";
     write;
   }

2. Then run this as follows:

   % grib_filter -o out.grib my.filter in.grib

   Of course you can make the IF condition more complicated e.g. select a range of messages to be copied:

   if (count == 3 || count == 13) {
     write;  # Write out message 3 and 13 only
   }

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