eccodes/examples/C/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.
 */

/*
 * C Implementation: grib_set_keys
 *
 * 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, "rb");
    if (!in) {
        fprintf(stderr, "Error: unable to open file %s\n", infile);
        return 1;
    }

    out = fopen(outfile, "wb");
    if (!out) {
        fprintf(stderr, "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) {
        fprintf(stderr, "Error: unable to create handle from file %s\n", infile);
        fclose(out);
        return 1;
    }

    /* 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;
}