Re: [netcdfgroup] problem reading array of strings in F90/C

• To: Dave Allured - NOAA Affiliate <dave.allured@xxxxxxxx>
• Subject: Re: [netcdfgroup] problem reading array of strings in F90/C
• From: M P <mzp3769@xxxxxxxxx>
• Date: Fri, 21 Oct 2022 10:16:14 -0600

Thanks for the tip, looks like a good starting point,
Mark

On Fri, Oct 21, 2022 at 9:20 AM Dave Allured - NOAA Affiliate <
dave.allured@xxxxxxxx> wrote:

> MP, download a copy of the netcdf-c source code.  In the test directories,
> I think there are valid working examples of reading and writing string
> arrays with C.  In particular, look for files tst_string*.c.  This should
> get you started.
>
> If desired, you can then write a fortran-callable C routine that reads
> string arrays, using a memory structure of your own choice.
>
>
> On Thu, Oct 20, 2022 at 12:34 PM M P <mzp3769@xxxxxxxxx> wrote:
>
>> Hello,
>> From this group's archive and searches I figured that reading those with
>> f90 is probably
>> not possible. I wrote a simple code in C but that also is not successful.
>> Can you help with solving this problem?
>> Thanks,
>> Mark
>>
>> netcdf file (datetime elements always 20 chars)
>> ....
>>
>>         int nlocs(nlocs) ;
>>                 nlocs:suggested_chunk_dim = 429LL ;
>> ....
>> group: MetaData {
>>   variables:
>>         string datetime(nlocs) ;
>>                 string datetime:_FillValue = "" ;
>>                 string datetime:units = "" ;
>>
>>
>> ncdump -v  datetime file.nc
>> .......
>>   datetime = "2021-09-30T23:02:25Z", "2021-09-30T23:07:25Z",
>>       "2021-09-30T23:09:23Z", "2021-09-30T23:17:25Z",
>> "2021-09-30T23:19:22Z",
>> .......
>>
>> C code: (nlocs, length=20 are set to correct values)
>> ...
>>   int status;
>> ..
>>   size_t start[] = {0,0};
>>   size_t count[] = {nlocs,length+1};
>>
>>   char datetime[nlocs][length+1];
>>   char *datetime_p[nlocs];
>>
>> ...
>>   for (i = 0; i < nlocs; i++)
>>     datetime_p[i] = datetime[i];
>> ...
>>   if ((status = nc_get_vara_string(grpid, varid, start, count,
>>                                    datetime_p)))
>>     ERR(status);
>> /* Error: NetCDF: Start+count exceeds dimension bound */
>>
>>   if ((status = nc_get_vara(grpid, varid, start, count,
>>                                    datetime_p)))
>>     ERR(status);
>> /* Error: NetCDF: Start+count exceeds dimension bound* /
>>
>>   if ((status = nc_get_var(grpid, varid, datetime_p)))
>>     ERR(status);
>> /* values in array are garbage */
>>
>>   if ((status = nc_get_var(grpid, varid, &datetime[0][0])))
>>     ERR(status);
>> /* values in array are garbage */
>> ........
>>
>> f90 code:
>> .......
>> INTEGER, PARAMETER :: date_string_length=20
>> CHARACTER(len=date_string_length), ALLOCATABLE :: aertimestr(:)
>> .......
>>
>> CALL check_nc(nf90_inq_grp_ncid(ncid,"MetaData",grpid))
>> CALL check_nc(nf90_inq_varid(grpid,"datetime",varid))
>> CALL check_nc(nf90_get_var(grpid,varid,aertimestr))
>>
>> .......
>> Error:
>> NetCDF: Attempt to convert between text & numbers
>>
>

• References:
  • [netcdfgroup] problem reading array of strings in F90/C
    • From: M P
  • Re: [netcdfgroup] problem reading array of strings in F90/C
    • From: Dave Allured - NOAA Affiliate