Re: 20011205: NF_PUT_ATT

>To: address@hidden
>From: Boyin Huang <address@hidden>
>Subject: NF_PUT_ATT
>Organization: UCAR/Unidata
>Keywords: 200112052104.fB5L4oN16859

Hi Boyin,

> I just started to use Fortran to generate NetCDF data
> file. I find I can not write the attribute into the
> file, although I tried to follow the instructions in
> the manual. Otherwise, everything seems fine:
> coordinate variables, dimensions, and data are all
> fine by using ncdump. The program stops at
> NF_PUT_ATT_type.
> I tried different types as shown below.
> 
> Looking forward to seeing your comments.
> 
> Boyin Huang at MIT
> 
> -----------------------------------
> 
> Here are the fortran lines:
> 
> c 1. create file
> 
> 
> status = nf_create('TOM_bmrc_con.nc', NF_CLOBBER,
> mcid)
> if(status.ne.NF_NOERR) stop 'create'
> 
> c 2. define dimension
> 
> status = nf_def_dim(mcid, 'longitude', idim, id_lon)
> if(status.ne.NF_NOERR) stop 'def_lon'
> status = nf_def_dim(mcid, 'latitude',  jdim, id_lat)
> if(status.ne.NF_NOERR) stop 'def_lat'
> status = nf_def_dim(mcid, 'depth',    kdim, id_depth)
> if(status.ne.NF_NOERR) stop 'def_dep'
> status = nf_def_dim(mcid, 'time',4  ,id_time)
> if(status.ne.NF_NOERR) stop 'def_time'
> 
> c 3. define variable
> 
> id_var_dim(1) = id_lon
> id_var_dim(2) = id_lat
> id_var_dim(3) = id_depth
> id_var_dim(4) = id_time
> 
> status
> =nf_def_var(mcid,'longitude',NF_double,1,id_lon,
> id_xx)
> if(status.ne.NF_NOERR) stop 'def_xx'
> status =
> nf_def_var(mcid,'latitude',NF_double,1,id_lat,        id_yy)
> if(status.ne.NF_NOERR) stop 'def_yy'
> status =
> nf_def_var(mcid,'depth',NF_double,1,id_depth,id_zz)
> if(status.ne.NF_NOERR) stop 'def_zz'
> status = nf_def_var(mcid,'time',NF_double,1,id_time
> ,id_tt)
> if(status.ne.NF_NOERR) stop 'def_tt'
> status = nf_def_var(mcid, 'to_c', NF_REAL, 4,
> id_var_dim, id_to)
> if(status.ne.NF_NOERR) stop 'def_var'
> 
> c 4. put attibute
> 
> print*,mcid,id_zz
> 
> status =
> NF_PUT_ATT_TEXT(mcid,NF_GLOBAL,'CMIPdata',4,'BMRC')
> if(status.ne.NF_NOERR) stop 'att_go'
> 
> status = nf_put_att_Real(mcid,id_to,'missing value'
>      1                                ,NF_real,1,1.e20)
> if(status.ne.NF_NOERR) stop 'att_to'

This will return an error status, because blanks are not permitted in
the names of netCDF attributes, dimensions, or variables, as specified
in section 2.1.1 Naming Conventions:

  The names of dimensions, variables and attributes consist of
  arbitrary sequences of alphanumeric characters (as well as
  underscore '_' and hyphen '-'), beginning with a letter or
  underscore. (However names commencing with underscore are reserved
  for system use.) Case is significant in netCDF names.

Since the manual was written, the character "." is also now permitted
in a name, but blank is not.  So try naming your attribute
"missing_value" instead of "missing value".

Another tip: use the "nf_strerror()" function to print error messages
for non-zero status returns, as in:

      status = nf_put_att_Real(mcid,id_to,'missing value'
     1     ,NF_real,1,1.e20)
      if(status.ne.NF_NOERR) then
         print *, nf_strerror(status)
         stop 'att_to'
      endif

This would print out

   Attribute or variable name contains illegal characters                       
   
  STOP: att_to

You could also encapsulate these error checks in a "handle_err()"
function, as in the example in section 5.2 describing nf_strerror().

--Russ

_____________________________________________________________________

Russ Rew                                         UCAR Unidata Program
address@hidden                     http://www.unidata.ucar.edu