Description
This example shows: how to create a multi field message in memory and write it in a file. The multi field messages can be created only in GRIB edition 2.
Source code
grib_multi_write.f90
! (C) Copyright 2005- ECMWF. ! ! This software is licensed under the terms of the Apache Licence Version 2.0 ! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. ! ! In applying this licence, ECMWF does not waive the privileges and immunities granted to it by ! virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. ! ! ! ! Description: how to create a multi field message in memory and write ! it in a file. The multi field messages can be created ! only in GRIB edition 2. ! ! ! program grib2_multi_write use eccodes implicit none integer :: infile,outfile integer :: in_gribid integer :: multi_gribid integer :: step,startsection ! multi field messages can be created only in edition 2 call codes_open_file(infile,'../../data/sample.grib2','r') call codes_open_file(outfile,'multi_created.grib2','w') ! a grib message is loaded from file ! in_gribid is the grib id to be used in subsequent calls call codes_grib_new_from_file(infile,in_gribid) startsection=4 do step=0,240,12 call codes_set(in_gribid,"step",step) call codes_grib_multi_append(in_gribid,startsection,multi_gribid) enddo ! write messages to a file call codes_grib_multi_write(multi_gribid,outfile) call codes_release(in_gribid) call codes_release(multi_gribid) call codes_close_file(infile) call codes_close_file(outfile) end program grib2_multi_write
grib_multi_write.py
# # (C) Copyright 2005- ECMWF. # # This software is licensed under the terms of the Apache Licence Version 2.0 # which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. # # In applying this licence, ECMWF does not waive the privileges and immunities # granted to it by virtue of its status as an intergovernmental organisation # nor does it submit to any jurisdiction. # import traceback import sys from eccodes import * INPUT = '../../data/sample.grib2' OUTPUT = 'out.mw.grib' VERBOSE = 1 # verbose error reporting def example(): fin = open(INPUT, 'rb') fout = open(OUTPUT, 'wb') gid = codes_grib_new_from_file(fin) mgid = codes_grib_multi_new() for step in range(12, 132, 12): codes_set(gid, "step", step) codes_grib_multi_append(gid, 4, mgid) codes_grib_multi_write(mgid, fout) codes_grib_multi_release(mgid) codes_release(gid) fin.close() fout.close() def main(): try: example() except CodesInternalError as err: if VERBOSE: traceback.print_exc(file=sys.stderr) else: sys.stderr.write(err.msg + '\n') return 1 if __name__ == "__main__": sys.exit(main())
grib_multi_write.c
/* * (C) Copyright 2005- ECMWF. * * This software is licensed under the terms of the Apache Licence Version 2.0 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. * * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction. */ /* * C Implementation: grib_multi_write * * Description: How to encode GRIB2 messages containing multiple fields * */ #include <stdio.h> #include <stdlib.h> #include <assert.h> #include "eccodes.h" static void usage(const char* prog) { printf("usage: %s in.grib out.grib\n",prog); exit(1); } int main(int argc, char** argv) { int err = 0; FILE* in = NULL; FILE* of = NULL; long edition, step; char* filename=NULL; char* ofilename=NULL; codes_handle *h = NULL; codes_multi_handle *mh=NULL; const int start_section = 4; /* Grib2 Product Definition Section */ if (argc < 3) usage(argv[0]); filename=argv[1]; ofilename=argv[2]; /* open input file */ in = fopen(filename,"r"); if(!in) { fprintf(stderr, "ERROR: unable to open input file %s\n",filename); return 1; } /* new grib handle from input file */ h = codes_handle_new_from_file(0, in, PRODUCT_GRIB, &err); CODES_CHECK(err,0); CODES_CHECK(codes_get_long(h,"edition",&edition),0); if (edition != 2) { fprintf(stderr, "ERROR: Input grib must be edition 2 for multi fields\n"); exit(1); } /* create a new empty multi field handle */ mh=codes_grib_multi_handle_new(0); if (!mh) { fprintf(stderr,"ERROR: Unable to create multi field handle\n"); exit(1); } for (step=12;step<=120;step+=12) { /* set step */ codes_set_long(h,"step",step); /* append h to mh repeating from section 4 */ /* i.e. starting from section 4 all the sections to the end of the message will be copied */ codes_grib_multi_handle_append(h, start_section, mh); } /* open output file */ of=fopen(ofilename,"w"); if(!of) { fprintf(stderr, "ERROR: unable to open output file %s\n",ofilename); exit(1); } /* write multi fields handle to output file */ codes_grib_multi_handle_write(mh,of); fclose(of); /* release memory */ codes_handle_delete(h); codes_grib_multi_handle_delete(mh); fclose(in); return 0; }