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[netCDF #OUJ-228033]: Netcdf library state?

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  • Subject: [netCDF #OUJ-228033]: Netcdf library state?
  • Date: Thu, 03 May 2012 16:47:53 -0600
Hi Willie,

> I am using a computer in which the netcdf library has aleady been
> built.  How do I find out whether it is a 64 bit library or a 32 bit
> library (I am not talking  about whether 64 bit offsets are used in the
> data file)?  My application can be built on 32 bit or 64 bit machines,
> but I obviously need to align this with the existing library, so I don't
> get run time parameter mismatches.

If you're using a Unix system, the "file" command can tells you for a shared 
library, as in:

  $ file /usr/local/lib/libnetcdf.so.7.2.0
  /usr/local/lib/libnetcdf.so.7.2.0: ELF 64-bit LSB shared object, x86-64, 
version 1 (SYSV), dynamically linked, not stripped

which indicates a 64-bit library.

For a static library archive, such as libnetcdf.a, that doesn't work:

  $ file /usr/local/lib/libnetcdf.a
  /usr/local/lib/libnetcdf.a: current ar archive

but you can still find out by extracting a member of the library and 
using "file" on that.  For example:

  $ ar t /usr/local/lib/libnetcdf.a | head -3
  libnetcdf_la-stub.o
  libnetcdf2_la-dv2i.o
  libdispatch_la-datt.o

tells you the first 3 members of the archive, and if you just pick one
and pipe it into the file command, voila:

  $ ar -p /usr/local/lib/libnetcdf.a libnetcdf_la-stub.o | file -
  /dev/stdin: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped

telling you it's a 64-bit object.

> A secondary question: is it possible to have both types of library of
> the same machine

Yes, for some Unix systems.  For example MacOS-X supports creating so-called 
"Universal" libraries that have 32-bit and 64-bit objects in the same library.
I don't think that's possible on Linux systems, and I'm not sure about other
platforms.

--Russ

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



Ticket Details
===================
Ticket ID: OUJ-228033
Department: Support netCDF
Priority: Normal
Status: Closed