Description

This example shows: how to set key values in GRIB messages

Source code

grib_set_keys.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 set key values in GRIB messages
!
!
program set
  use eccodes
  implicit none
  integer(kind = 4)    :: centre, date1
  integer              :: infile,outfile
  integer              :: igrib
  character(len=12)    :: marsType = 'ses'

  centre = 80
  call current_date(date1)
  call codes_open_file(infile, '../../data/regular_latlon_surface_constant.grib1','r')
  call codes_open_file(outfile, 'out.set.grib1','w')

  ! A new GRIB message is loaded from file
  ! igrib is the grib id to be used in subsequent calls
  call codes_grib_new_from_file(infile,igrib)

  call codes_set(igrib,'dataDate',date1)
  call codes_set(igrib,'type', marsType)

  !     set centre as a integer */
  call codes_set(igrib,'centre',centre)

  ! Check if it is correct in the actual GRIB message
  call check_settings(igrib)

  ! Write modified message to a file
  call codes_write(igrib,outfile)

  call codes_release(igrib)

  call codes_close_file(infile)
  call codes_close_file(outfile)

contains

!======================================
subroutine current_date(date1)
integer, intent(out) :: date1

integer              :: val_date(8)
call date_and_time ( values = val_date)

date1 = val_date(1)* 10000 + val_date(2)*100 + val_date(3)
end subroutine current_date
!======================================
subroutine check_settings(gribid)
  implicit none
  integer, intent(in) :: gribid

  integer(kind = 4)    :: int_value
  character(len = 10)  :: string_value

  !     get centre as a integer
  call codes_get(gribid,'centre',int_value)
  write(*,*) "get centre as a integer - centre = ",int_value

  !     get centre as a string
  call codes_get(gribid,'centre',string_value)
  write(*,*) "get centre as a string  - centre = ",string_value

  !     get date as a string
  call codes_get(gribid,'dataDate',string_value)
  write(*,*) "get date as a string    - date = ",string_value

end subroutine check_settings
end program set
grib_set_keys.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.
#
# Description: how to set key values in GRIB messages
#

import traceback
import sys

from eccodes import *
from datetime import date
from collections import OrderedDict

INPUT = '../../data/regular_latlon_surface_constant.grib1'
OUTPUT = 'out.set.grib'
VERBOSE = 1  # verbose error reporting


def example():
    fin = open(INPUT, 'rb')
    fout = open(OUTPUT, 'wb')
    gid = codes_grib_new_from_file(fin)

    dt = date.today()
    today = "%d%02d%02d" % (dt.year, dt.month, dt.day)
    codes_set(gid, 'dataDate', int(today))
    codes_set(gid, 'centre', 80)

    centreIntVal = codes_get_array(gid, 'centre', int)
    centreStrVal = codes_get_array(gid, 'centre', str)
    dateStrVal = codes_get_array(gid, 'dataDate', str)
    assert (centreIntVal[0] == 80)
    assert (centreStrVal[0] == 'cnmc')
    assert (dateStrVal[0] == today)
    print('get centre as an integer - centre = %d' % centreIntVal[0])
    print('get centre as a string - centre = %s' % centreStrVal[0])
    print('get date as a string - date = %s' % dateStrVal[0])

    # Now do the same but using set_key_vals, setting keys all at once
    print('set keys using one long comma-separated string...')
    codes_set_key_vals(gid, 'level=1,centre=98')
    assert (codes_get(gid, 'centre', str) == 'ecmf')
    assert (codes_get(gid, 'level', int) == 1)

    print('set keys using a list of strings...')
    codes_set_key_vals(gid, ['level=2', 'centre=kwbc'])
    assert (codes_get(gid, 'centre', int) == 7)
    assert (codes_get(gid, 'level', int) == 2)

    print('set keys using a dictionary (order not as specified!)...')
    codes_set_key_vals(gid, {'level': 3, 'centre': 84})
    assert (codes_get(gid, 'centre', str) == 'lfpw')
    assert (codes_get(gid, 'level', int) == 3)

    print('set keys using an ordered dictionary...')
    codes_set_key_vals(gid, OrderedDict([('level', 3), ('centre', 84)]))
    assert (codes_get(gid, 'centre', str) == 'lfpw')
    assert (codes_get(gid, 'level', int) == 3)

    codes_gts_header(True)
    codes_gts_header(False)

    codes_write(gid, fout)
    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_set_keys.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.
 */

/*
 * Description: how to set key values in GRIB messages
 *
 */
#include <stdio.h>
#include <stdlib.h>

#include "eccodes.h"

int main(int argc, char** argv)
{
    int err = 0;
    long centre=80;
    long long_value=0;
    char string_value[100];
    size_t len = sizeof(string_value)/sizeof(char);
    size_t size=0;

    FILE* in = NULL;
    const char* infile = "../../data/regular_latlon_surface.grib1";
    FILE* out = NULL;
    const char* outfile = "out.set.grib1";
    codes_handle *h = NULL;
    const void* buffer = NULL;
    size_t str_len = 0; /* See the call to codes_set_string later */

    in = fopen(infile,"r");
    if(!in) {
        printf("ERROR: unable to open file %s\n",infile);
        return 1;
    }

    out = fopen(outfile,"w");
    if(!out) {
        printf("ERROR: unable to open file %s\n",outfile);
        fclose(in);
        return 1;
    }

    /* create a new handle from a message in a file */
    h = codes_handle_new_from_file(0, in, PRODUCT_GRIB, &err);
    if (h == NULL) {
        printf("Error: unable to create handle from file %s\n",infile);
    }

    /* set centre as a long */
    CODES_CHECK(codes_set_long(h,"centre",centre),0);

    /* set paramId and shortName - normally you would do one or the other */
    CODES_CHECK(codes_set_long(h,"paramId", 500004),0);
    /* the value of str_len is not used, it can be anything! */
    CODES_CHECK(codes_set_string(h,"shortName", "fis", &str_len),0);

    /* get centre as a long */
    CODES_CHECK(codes_get_long(h,"centre",&long_value),0);
    printf("centre long value=%ld\n",long_value);

    /* get centre as a string */
    CODES_CHECK(codes_get_string(h,"centre",string_value,&len),0);
    printf("centre string value=%s\n",string_value);

    /* get the coded message in a buffer */
    CODES_CHECK(codes_get_message(h,&buffer,&size),0);

    /* write the buffer in a file*/
    if(fwrite(buffer,1,size,out) != size)
    {
        perror(outfile);
        exit(1);
    }

    codes_handle_delete(h);
    fclose(in);
    fclose(out);

    return 0;
}