NetCDF  4.8.1
simple_nc4_wr.c
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1 /* Copyright 2019 University Corporation for Atmospheric
2  Research/Unidata. See COPYRIGHT file for conditions of use. */
18 #include <stdlib.h>
19 #include <stdio.h>
20 #include <netcdf.h>
21 
22 /* This is the name of the data file we will create. */
23 #define FILE_NAME "simple_nc4.nc"
24 
25 /* We are writing 2D data, a 6 x 12 grid. */
26 #define NDIMS 2
27 #define NX 6
28 #define NY 12
29 
30 /* Handle errors by printing an error message and exiting with a
31  * non-zero status. */
32 #define ERRCODE 2
33 #define ERR(e) {printf("Error: %s\n", nc_strerror(e)); exit(ERRCODE);}
34 
35 int
36 main()
37 {
38  /* When we create netCDF variables, groups, dimensions, or types,
39  * we get back an ID for each one. */
40  int ncid, x_dimid, y_dimid, varid1, varid2, grp1id, grp2id, typeid;
41  int dimids[NDIMS];
42 
43  /* This is the data array we will write. It will be filled with a
44  * progression of numbers for this example. */
45  unsigned long long data_out[NX][NY];
46 
47  /* Loop indexes, and error handling. */
48  int x, y, retval;
49 
50  /* The following struct is written as a compound type. */
51  struct s1
52  {
53  int i1;
54  int i2;
55  };
56  struct s1 compound_data[NX][NY];
57 
58  /* Create some pretend data. */
59  for (x = 0; x < NX; x++)
60  for (y = 0; y < NY; y++)
61  {
62  data_out[x][y] = x * NY + y;
63  compound_data[x][y].i1 = 42;
64  compound_data[x][y].i2 = -42;
65  }
66 
67  /* Create the file. The NC_NETCDF4 flag tells netCDF to
68  * create a netCDF-4/HDF5 file.*/
69  if ((retval = nc_create(FILE_NAME, NC_NETCDF4|NC_CLOBBER, &ncid)))
70  ERR(retval);
71 
72  /* Define the dimensions in the root group. Dimensions are visible
73  * in all subgroups. */
74  if ((retval = nc_def_dim(ncid, "x", NX, &x_dimid)))
75  ERR(retval);
76  if ((retval = nc_def_dim(ncid, "y", NY, &y_dimid)))
77  ERR(retval);
78 
79  /* The dimids passes the IDs of the dimensions of the variable. */
80  dimids[0] = x_dimid;
81  dimids[1] = y_dimid;
82 
83  /* Define two groups, "grp1" and "grp2." */
84  if ((retval = nc_def_grp(ncid, "grp1", &grp1id)))
85  ERR (retval);
86  if ((retval = nc_def_grp(ncid, "grp2", &grp2id)))
87  ERR (retval);
88 
89  /* Define an unsigned 64bit integer variable in grp1, using dimensions
90  * in the root group. */
91  if ((retval = nc_def_var(grp1id, "data", NC_UINT64, NDIMS,
92  dimids, &varid1)))
93  ERR(retval);
94 
95  /* Write unsigned long long data to the file. For netCDF-4 files,
96  * nc_enddef will be called automatically. */
97  if ((retval = nc_put_var_ulonglong(grp1id, varid1, &data_out[0][0])))
98  ERR(retval);
99 
100  /* Create a compound type. This will cause nc_reddef to be called. */
101  if (nc_def_compound(grp2id, sizeof(struct s1), "sample_compound_type",
102  &typeid))
103  ERR(retval);
104  if (nc_insert_compound(grp2id, typeid, "i1",
105  offsetof(struct s1, i1), NC_INT))
106  ERR(retval);
107  if (nc_insert_compound(grp2id, typeid, "i2",
108  offsetof(struct s1, i2), NC_INT))
109  ERR(retval);
110 
111  /* Define a compound type variable in grp2, using dimensions
112  * in the root group. */
113  if ((retval = nc_def_var(grp2id, "data", typeid, NDIMS,
114  dimids, &varid2)))
115  ERR(retval);
116 
117  /* Write the array of struct to the file. This will cause nc_endef
118  * to be called. */
119  if ((retval = nc_put_var(grp2id, varid2, &compound_data[0][0])))
120  ERR(retval);
121 
122  /* Close the file. */
123  if ((retval = nc_close(ncid)))
124  ERR(retval);
125 
126  printf("*** SUCCESS writing example file simple_nc4.nc!\n");
127  return 0;
128 }
nc_def_compound
EXTERNL int nc_def_compound(int ncid, size_t size, const char *name, nc_type *typeidp)
Definition: dcompound.c:63
nc_def_var
EXTERNL int nc_def_var(int ncid, const char *name, nc_type xtype, int ndims, const int *dimidsp, int *varidp)
Define a new variable.
Definition: dvar.c:212
nc_insert_compound
EXTERNL int nc_insert_compound(int ncid, nc_type xtype, const char *name, size_t offset, nc_type field_typeid)
Definition: dcompound.c:99
nc_def_dim
EXTERNL int nc_def_dim(int ncid, const char *name, size_t len, int *idp)
Define a new dimension.
Definition: ddim.c:121
NC_INT
#define NC_INT
signed 4 byte integer
Definition: netcdf.h:38
nc_put_var_ulonglong
int nc_put_var_ulonglong(int ncid, int varid, const unsigned long long *op)
Definition: dvarput.c:998
nc_put_var
EXTERNL int nc_put_var(int ncid, int varid, const void *op)
Definition: dvarput.c:920
nc_close
EXTERNL int nc_close(int ncid)
Definition: dfile.c:1291
netcdf.h
nc_def_grp
EXTERNL int nc_def_grp(int parent_ncid, const char *name, int *new_ncid)
Define a new group.
Definition: dgroup.c:268
NC_UINT64
#define NC_UINT64
unsigned 8-byte int
Definition: netcdf.h:46
NC_NETCDF4
#define NC_NETCDF4
Use netCDF-4/HDF5 format.
Definition: netcdf.h:152
nc_create
EXTERNL int nc_create(const char *path, int cmode, int *ncidp)
Definition: dfile.c:389
NC_CLOBBER
#define NC_CLOBBER
Destroy existing file.
Definition: netcdf.h:128