Re: question of char

• To: mazurier <mazurier@xxxxxxx>
• Subject: Re: question of char
• From: Russ Rew <russ@xxxxxxxxxxxxxxxx>
• Date: Mon, 28 Feb 2000 08:25:59 -0700

Hi Alain,

> I would like to create a netcdf file with a variable
> containing two strings which it is like this example
> 
> 
> netcdf fileTOTO {
> dimensions:
>         nbData = UNLIMITED ; // (X currently)
>         numberOfChar = 255 ;
>         numberOfField = 2 ;
> variables:
>         char COD_CAPTEUR(?????) ;
> data:
> 
>  COD_CAPTEUR
>   "hello world","hello USA"
>   "hello France","hello Russ"
>   "xxxxx" "xxxxx"
>    ....
>   "xxxxx" "xxxxx";
> 
> I don't know how to declare my variable and if it possible ?
> I'am using C++ with netcdf-3.4 on Sun Solaris 2.6.

NetCDF supports multidimensional character arrays rather than arrays
of strings, so if your strings are of different lengths, it will waste
some space.  If the maximum length of strings in the COD_CAPTEUR
variable is 20, for example, add an extra "stringlen" dimension of
length 20:

 netcdf fileTOTO {
 dimensions:
         nbData = UNLIMITED ; // (X currently)
         numberOfChar = 255 ;
         numberOfField = 2 ;
         stringlen = 20;
 variables:
         char COD_CAPTEUR(nbData, stringlen) ;
 data:

  COD_CAPTEUR
   "hello world","hello USA",
   "hello France","hello Russ",
   "xxxxx", "xxxxx";
 }

The ncdump and ncgen utilities honor the C convention of
null-terminated strings in such arrays.  In other words, if you create
a binary netCDF file from the above using "ncgen -b ..." and then
ncdump the resulting file, it will preserve the strings, but what is
stored in the file is still a rectangular array of characters.

--Russ

_____________________________________________________________________

Russ Rew                                         UCAR Unidata Program
russ@xxxxxxxxxxxxxxxx                     http://www.unidata.ucar.edu

• References:
  • question of char
    • From: mazurier