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Re: 20020718: ncopen

>To: address@hidden
>From: Mimi Lee <address@hidden>
>Subject: ncopen
>Organization: UCLA
>Keywords: 200207180254.g6I2suH04290

Mimi,

> First of all, I would like to thank you for such prompt response.  I
> was able to find the v2i.c file at /src/librc directory. but it's
> subsequent files for lnetcdf which is esstial for ncopen is no where
> to be found. below is the output msg.
> 
> The end result in bin, lib, and include directory is
> lib/
> libnetcdf.a      libnetcdf_c++.a
> 
> inlcude/
> ncvalues.h   netcdfcpp.h  netcdf.h     netcdf.hh    netcdf.inc   NETCDF.mod
> 
> bin/
> ncdump  ncgen
> 
> As you can see, only ncdump and ncgen are being generated and if you
> can scroll down and see the error msg, "for ncopen in -lnetcdf"
> doesn't not exist.  I know I must be missing something here ...

ncdump and ncgen are the only executables that should be in the bin/
directory, since they are the only programs that come with the netCDF
distribution.  They are utility programs, used to convert between
binary netCDF data and a text representation of the data.

"ncopen" is a library function that should be part of the libnetcdf.a
archive in the lib/ directory.  "-lnetcdf" is just a shortcut for
specifying the library "libnetcdf.a" to a linker or compiler, assuming
it has the directory containing that library archive in its list of
which directories to search.  So, for example, if libnetcdf.a was
stored in the /usr/local/netcdf/lib/ directory, a compiler might be
instructed to look there and use the netCDF library with the arguments

  -L/usr/local/netcdf/lib -lnetcdf

or by including that directory in a LD_LIBRARY_PATH environment
variable.

It is possible that the libnetcdf.a you have was built to explicitly
not include the netCDF version 2 interfaces (ncopen is a version 2
netCDF interface) if someone built it with the macro "NO_NETCDF_2"
defined, for example using the compiler flag "-DNO_NETCDF_2".
Otherwise, all the version 2 interfaces including ncopen are included
in the library by default.

You can check whether ncopen is in your libnetcdf.a archive by using
the "nm" program, using something like:

  % cd lib       # change to the lib/ directory containing libnetcdf.a
  % nm -A libnetcdf.a | grep ncopen

and you should see output something like

  libnetcdf.a[v2i.o]: [23]      |       356|      72|FUNC |GLOB |0    |2      
|ncopen
  libnetcdf.a[fort-v2compat.o]: [84]    |         0|       0|FUNC |GLOB |0    
|UNDEF  |ncopen

the first line indicating "ncopen" is a global symbol defined in the
v2i.o module in the library, and the second line indicating ncopen is
referenced in the fort-v2compat.o module also in the library.  The
second line may not appear if your library was not built to support a
Fortran interface.  The format of these lines and specific numbers
may differ depending on platform, but "ncopen" is there if any line
similar to the first above appears in the output.

If there is no "ncopen" line in the output of "nm", then someone built
your library with "-DNO_NETCDF_2" included in the CFLAGS or CPPFLAGS
environment variable before running the configure script.  In that
case, you will have to rebuild the netCDF library from source,
omitting that macro definition from your CFLAGS or CPPFLAGS
environment variables before building.  Instructions for building from
scratch are in the INSTALL.html file at

  http://www.unidata.ucar.edu/packages/netcdf/INSTALL.html

--Russ

_____________________________________________________________________

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