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3.2 Specifying the Environment for Building

The netCDF configure script searches your path to find the compilers and tools it needed. To use compilers that can't be found in your path, set their environment variables.

When finding compilers, vendor compilers will be preferred to GNU compilers. Not because we don't like GNU, but because we assume if you purchased a compiler, you want to use it. Setting CC allows you to over-ride this preference. (Alternatively, you could temporarily remove the compiler's directories from your PATH.)

For example, on an AIX system, configure will first search for xlc, the AIX compiler. If not found, it will try gcc, the GNU compiler. To override this behavior, set CC to gcc (in sh: export CC=gcc). (But don't forget to also set CXX to g++, or else configure will try and use xlC, the AIX C++ compiler to build the netCDF C++ API.)

By default, the netCDF library is built with assertions turned on. If you wish to turn off assertions, set CPPFLAGS to -DNDEBUG (csh ex: setenv CPPFLAGS -DNDEBUG).

If GNU compilers are used, the configure script sets CPPFLAGS to “-g -O2”. If this is not desired, set CPPFLAGS to nothing, or to whatever other value you wish to use, before running configure.

For cross-compiles, the following environment variables can be used to override the default fortran/C type settings like this (in sh): 

     export NCBYTE_T=''integer(selected_int_kind(2))''
     export NCSHORT_T=''integer*2''
     export NF_INT1_T=''integer(selected_int_kind(2))''
     export NF_INT2_T=''integer*2''
     export NF_INT1_IS_C_SHORT=1
     export NF_INT2_IS_C_SHORT=1
     export NF_INT_IS_C_INT=1
     export NF_REAL_IS_C_FLOAT=1
     export NF_DOUBLEPRECISION_IS_C_DOUBLE=1

In this case you will need to run configure with –disable-fortran-compiler-check and –disable-fortran-type-check.

3.2.1 Variable Description Notes

CC C compiler If you don't specify this, the configure script will try to find a suitable C compiler such as cc, c89, xlc, or gcc.


FC Fortran compiler (if any) If you don't specify this, the configure script will try to find a suitable Fortran and Fortran 77 compiler. Set FC to "" explicitly, or provide the –disable-f77 option to configure, if no Fortran interface is desired. Use –disable-f90 to disable the netCDF Fortran 90 API, but build the netCDF Fortran 77 API.


F77 Fortran 77 compiler (if any) Only specify this if your platform explicitly needs a different Fortran 77 compiler. Otherwise use FC to specify the Fortran compiler. If you don't specify this, the configure script will try to find a suitable Fortran compiler. For vendor compilers, make sure you're using the same vendor's Fortran 90 compiler. Using Fortran compilers from different vendors, or mixing vendor compilers with g77, the GNU F77 compiler, is not supported and may not work.


CXX C++ compiler If you don't specify this, the configure script will try to find a suitable C++ compiler. Set CXX to "" explicitly, or use the –disable-cxx configure option, if no C++ interface is desired. If using a vendor C++ compiler, use that vendor's C compiler to compile the C interface. Using different vendor compilers for C and C++ may not work.


CFLAGS C compiler flags "-O" or "-g", for example. If you don't set this, configure may set it based on your platform's needs (unless you have used the –disable-flag-setting option is used with configure).


CPPFLAGS C preprocessor options "-DNDEBUG" to omit assertion checks, for example. If you don't set this, configure may set it based on your platform's needs (unless you have used the –disable-flag-setting option is used with configure).


FCFLAGS Fortran 90 compiler flags "-O" or "-g", for example. These flags will be used for FORTRAN 90. If setting these you may also need to set FFLAGS for the FORTRAN 77 test programs.


FFLAGS Fortran 77 compiler flags "-O" or "-g", for example. If you need to pass the same arguments to the FORTRAN 90 build, also set FCFLAGS.


CXXFLAGS C++ compiler flags "-O" or "-g", for example. If you don't set this, configure may set it based on your platform's needs (unless you have used the –disable-flag-setting option is used with configure).


ARFLAGS, NMFLAGS, FPP, M4FLAGS, LIBS, FLIBS, FLDFLAGS Miscellaneous One or more of these were needed for some platforms, as specified below. Unless specified, you should not set these environment variables, because that may interfere with the configure script.


HDF5DIR configure option Set this to the directory you wish to specify in the –with-hdf5 argument of configure.

The section marked Tested Systems below contains a list of systems on which we have built this package, the environment variable settings we used, and additional commentary.