netcdf-c/examples/C/sfc_pres_temp_more.c

/* Copyright 2018 University Corporation for Atmospheric
   Research/Unidata.  See COPYRIGHT file for conditions of use. */
/**
 * @file
 * @ingroup tutorial
 * This is part of the netCDF package.
 *
 * This is a simple example which writes and then reads some surface
 * pressure and temperatures, and stores additional metadata as
 * dimension variables, and an attribute with a nice poem about data.
 *
 * @author Ed Hartnett started 2006/03/25, finished 2019/7/2
 */
#include <netcdf.h>
#include <stdlib.h>
#include <string.h>

#define FILE_NAME "sfc_pres_temp_more.nc"
#define NDIMS 2
#define LAT_NAME "latitude"
#define LAT_LEN 40
#define LON_NAME "longitude"
#define LON_LEN 80
#define PRES_NAME "surface_pressure"
#define TEMP_NAME "surface_temperature"
#define SONNET_NAME "Brownings_sonnet_mangled_by_Hartnett"

char poem[] = "How do I love data? Let me count the ways.\n"
    "I love data to the depth and breadth and height\n"
    "My model can reach, when running overnight\n"
    "From the ends of CONUS and ideal Space.\n"
    "I love data to the level of every day's\n"
    "6Z ob, by Sun and Linux box.\n"
    "I love data freely, as PIs strive for funding;\n"
    "I love data purely, as good C code is compiled,\n"
    "I love data with the passion put to use\n"
    "In my old programs, and with my childhood's TRS-80.\n"
    "I love data with a love I seemed to lose\n"
    "With my lost password -I love data with the constants,\n"
    "expressions, statements, of all my code! -and, if NSF choose,\n"
    "I shall love data better after processing.";

int
main()
{
    int ncid, lon_dimid, lat_dimid, pres_varid, temp_varid, lat_varid, lon_varid;
    int dimids[NDIMS];
    float pres_out[LAT_LEN][LON_LEN], pres_in[LAT_LEN][LON_LEN];
    float temp_out[LAT_LEN][LON_LEN], temp_in[LAT_LEN][LON_LEN];
    float latitude[LAT_LEN], longitude[LON_LEN];
    char *att_in;
    size_t len_in;
    int error = 0;
    int lat, lon, retval;

    /* Create phoney data. If this wasn't an example program, we would
     * have some real data to write, for example, model output. */
    for (lat = 0; lat < LAT_LEN; lat++)
        for (lon = 0; lon < LON_LEN; lon++)
        {
            pres_out[lat][lon] = 1013.1;
            temp_out[lat][lon] = 12.5;
        }

    /* These are the latitudes and longitudes which correspond with
     * ticks on the dimension axes. */
    for (lat = 0; lat < LAT_LEN; lat++)
        latitude[lat] = 40. + lat * 2.5;
    for (lon = 0; lon < LON_LEN; lon++)
        longitude[lon] = -90. - lon * 5;

    /* Create the file. */
    if ((retval = nc_create(FILE_NAME, NC_CLOBBER, &ncid)))
        return retval;

    /* Add data sonnet. By using NC_GLOBAL we mean that this attribute
     * applies to the entire file, not just to one variable. Don't
     * forget that strlen does not include the null terminator, so if
     * you want it, you need to add one more byte. */
    if ((retval = nc_put_att_text(ncid, NC_GLOBAL, SONNET_NAME,
                                  strlen(poem) + 1, poem)))
        return retval;

    /* Define the dimensions. */
    if ((retval = nc_def_dim(ncid, LAT_NAME, LAT_LEN, &lat_dimid)))
        return retval;
    if ((retval = nc_def_dim(ncid, LON_NAME, LON_LEN, &lon_dimid)))
        return retval;

    /* Save the dimension information, in variables of the same
     * name. First we need to define these variables. */
    dimids[0] = lat_dimid;
    if ((retval = nc_def_var(ncid, LAT_NAME, NC_FLOAT, 1, dimids, &lat_varid)))
        return retval;
    dimids[0] = lon_dimid;
    if ((retval = nc_def_var(ncid, LON_NAME, NC_FLOAT, 1, dimids, &lon_varid)))
        return retval;

    /* Define the variables. */
    dimids[0] = lat_dimid;
    dimids[1] = lon_dimid;
    if ((retval = nc_def_var(ncid, PRES_NAME, NC_FLOAT, NDIMS, dimids, &pres_varid)))
        return retval;
    if ((retval = nc_def_var(ncid, TEMP_NAME, NC_FLOAT, NDIMS, dimids, &temp_varid)))
        return retval;

    /* End define mode. */
    if ((retval = nc_enddef(ncid)))
        return retval;

    /* Write the dimension metadata. */
    if ((retval = nc_put_var_float(ncid, lat_varid, latitude)))
        return retval;
    if ((retval = nc_put_var_float(ncid, lon_varid, longitude)))
        return retval;

    /* Write the phoney data. */
    if ((retval = nc_put_var_float(ncid, pres_varid, (float *)pres_out)))
        return retval;
    if ((retval = nc_put_var_float(ncid, temp_varid, (float *)temp_out)))
        return retval;

    /* Close the file. */
    if ((retval = nc_close(ncid)))
        return retval;

    /* Open the file and check that everything's OK. */
    if ((retval = nc_open(FILE_NAME, 0, &ncid)))
        return retval;

    /* Read the attribute. First find it's length to allocate storage
     * for it. */
    if ((retval = nc_inq_attlen(ncid, NC_GLOBAL, SONNET_NAME, &len_in)))
        return retval;
    if (!(att_in = malloc(len_in)))
        return NC_ENOMEM;
    if ((retval = nc_get_att_text(ncid, NC_GLOBAL, SONNET_NAME, att_in)))
        return retval;
    if (strcmp(att_in, poem))
        error++;
    free(att_in);
    if (error)
        return -2;

    /* Read the data. */
    if ((retval = nc_get_var_float(ncid, pres_varid, (float *)pres_in)))
        return retval;
    if ((retval = nc_get_var_float(ncid, temp_varid, (float *)temp_in)))
        return retval;

    /* Check the data. */
    for (lat = 0; lat < LAT_LEN; lat++)
        for (lon = 0; lon < LON_LEN; lon++)
            if (pres_in[lat][lon] != pres_out[lat][lon] ||
                temp_in[lat][lon] != temp_out[lat][lon])
                return -2;

    /* Close the file. */
    if ((retval = nc_close(ncid)))
        return retval;

    return 0;
}