Building the NetCDF-4.2 and later Fortran libraries

[TOC]

In versions before 4.2, the Fortran netCDF library source was bundled with the C library source in one distribution. With more recent versions, the Fortran netCDF library has been split off into an independent source distribution, intended to be built as a separate library, after the C library is built and installed. This separation simplifies the building and use of the C and Fortran netCDF libraries and allows them to evolve independently.

More recently, building netcdf-fortran as an automated step in the netcdf-c build is now possible (for non-MSVC builds) by using new options at configure time, so if you haven't built and installed the netCDF-C library yet, you may want to try the new netCDF-C <a href="https://docs.unidata.ucar.edu/netcdf-c/current/getting_and_building_netcdf.html#getting"

Fortran-bootstrap procedure.

In the example commands below, we assume use of a POSIX-standard shell, such as sh, bash, ksh, or zsh. If you are using csh instead, you will have to use the

   setenv ENV_VARIABLE  value

syntax to set environment variables instead of the

   ENV_VARIABLE=value

syntax used in the examples. In either case, ${VAR} is the value of the shell variable or environment variable VAR.

It will be easier to build the netCDF Fortran library if the C (and if needed, HDF5) libraries are built as shared libraries (the default), but you can also use static libraries, as described in a later section.

Building with shared libraries

First make sure the netCDF C library has been built, tested, and installed. The shell variable NCDIR should be set such that the shared library for netCDF C is under ${NCDIR}/lib and netCDF utilities such as ncdump are under ${NCDIR}/bin. For example:
```
NCDIR=/usr/local
```
The configure script will try to determine suitable Fortran and C compilers for building netCDF Fortran, but you can instead specify them with the FC and CC environment variables, if needed. For example:
```
CC=/usr/local/cc
FC=/usr/local/fortran
```
If the netCDF C library was installed as a shared library in a location that is not searched by default, you will need to set the LD_LIBRARY_PATH environment variable (or DYLD_LIBRARY_PATH on OSX) to specify that directory before running the configure script. For example:
```
export LD_LIBRARY_PATH=${NCDIR}/lib:${LD_LIBRARY_PATH}
```
If you set the LD_LIBRARY_PATH (or DYLD_LIBRARY_PATH) environment variable in the previous step, don't use "sudo" before the following "configure" or "make check" commands. Using "sudo" causes the LD_* environment variables to be ignored. You can use "sudo make install" as the last step if necessary, but don't use "sudo" before that.
Set the shell variable NFDIR to where you want to install netCDF Fortran, which can be the same location where the netCDF C was installed (default /usr/local), but not the source directory where you are building the software. Then, from the top-level source directory, run the configure script, using CPPFLAGS and LDFLAGS to specify where the netCDF C library was installed:
```
NFDIR=/usr/local
CPPFLAGS=-I${NCDIR}/include LDFLAGS=-L${NCDIR}/lib \
./configure --prefix=${NFDIR}
```
If you are cross-compiling, you should also include the configure option "--disable-fortran-type-check", as in:
```
CPPFLAGS=-I${NCDIR}/include LDFLAGS=-L${NCDIR}/lib \
./configure --prefix=${NFDIR} --disable-fortran-type-check
```
To see other configure options, run configure --help.
If that succeeds, run
```
make check
```
If that succeeds, run
```
make install
```
or
```
sudo make install
```

If you encounter problems, send the complete "config.log" file generated by running configure to support-netcdf@unidata.ucar.edu.

Building with static libraries

If you can't build the C netCDF library as a shared library or if it has already been installed by someone else only as a static library (which means there are no libnetcdf.so files in the library directory where the netCDF C library was installed), then building and installing the Fortran netCDF libraries will be more complicated.

The configure script will try to determine suitable Fortran and C compilers for building netCDF Fortran, but you can also, specify them with the FC and CC environment variables.
Assume the static netCDF C library is installed under ${NCDIR}, the HDF5 library under ${H5DIR}, and other needed libraries such as zlib and curl under ${ODIR}. Some or all of these could be the same (for example /usr/local).
Let the shell variable ${NFDIR} specify where you want to install the netCDF Fortran library. This can be the same location where the netCDF C library is installed (default is /usr/local).
Set the CPPFLAGS, LDFLAGS, LD_LIBRARY_PATH, and LIBS environment variables to specify where the netCDF C library is installed and where the other libraries may be found. For example:
```
CPPFLAGS="-I${NCDIR}/include -I${H5DIR}/include -I${ODIR}/include" \
LDFLAGS="-L${NCDIR}/lib -L${H5DIR}/lib -L${ODIR}/lib" \
LD_LIBRARY_PATH=${NCDIR}/lib:${H5DIR}/lib:${ODIR}/lib \
LIBS="-lnetcdf -lhdf5_hl -lhdf5 -lz -lcurl" \
./configure --disable-shared --prefix=${NCDIR}
```
If you are cross-compiling, you should also include the configure option "--disable-fortran-type-check".
For parallel I/O: The configure script sets CFLAGS appropriately for standard compilers, but if you are building with parallel I/O using wrappers such as mpicc, mpif90, and mpif77, specify compilers using the CC, FC, and F77 variables before configure. For example:
```
CC=mpicc FC=mpif90 F77=mpif77 CPPFLAGS=-I${NCDIR}/include \
LDFLAGS=-L${NCDIR}/lib ./configure --prefix=${NFDIR}
```
You may have to use absolute path names for CC, F90, and F77 if configure can't find them. Finally, you may also need to set CFLAGS to indicate which Fortran compiler is wrapped by mpif90 nd mpif77. For example, if "mpif90 --show" indicates gfortran is being used, then set CFLAGS=-DgFortran, and similarly set CFLAGS=-DpgiFortran for Portland Group compilers.
If that succeeds, run "make check".
If that succeeds, run "make install" or "sudo make install".

If you encounter problems, send the complete "config.log" file generated by running configure to support-netcdf@unidata.ucar.edu.

Linking your programs with netCDF Fortran libraries

If you built the shared libraries, you can link with something like

fortran my_prog.f -o my_prog -I${NFDIR}/include -L${NFDIR}/lib -lnetcdff

to link your Fortran software with the installed netCDF Fortran and C libraries.

If you didn't install the shared libraries in a standard place, you may need to set LD_LIBRARY_PATH (or DYLD_LIBRARY_PATH for OSX) to include ${NFDIR}/lib before running the resulting program. Alternatively, you may add ${NFDIR}/lib to the LD_RUN_PATH environment variable before linking, or use the -Wl,-rpath -Wl,${NFDIR}/lib linker flag, or have your system administrator add ${NFDIR}/lib to `/etc/ld.so.conf'. See operating system documentation about shared libraries for more information, such as the ld(1) and ld.so(8) manual pages.

If you built static libraries, you will need to use something like

fortran my_prog.f -o my_prog -I${NFDIR}/include \
-L${NCDIR}/lib -lnetcdff -lnetcdf \
-L${H5DIR}/lib -lhdf5_hl -lhdf5 -L${ODIR} -lz -lcurl -lm

to link Fortran software with the installed Fortran library and the libraries on which it depends.

A simpler alternative that should work for either shared or static libraries is to use the "nf-config" utility installed in ${NFDIR}/bin:

fortran my_prog.f -o my_prog `nf-config --fflags --flibs`

or the more general "pkg-config" utility, if you have it:

fortran my_prog.f -o my_prog `pkg-config --cflags --libs netcdf-fortran`

Specifying The Environment for Building

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.

Environment Variable Description Notes

Variable	Usage	Description
CC	C compiler	If you don't specify this, the configure script will try to find a suitable C compiler. The default choice is gcc. If you wish to use a vendor compiler you must set CC to that compiler, and set other environment variables (as described below) to appropriate settings.
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. 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 is not supported and may not work.
CFLAGS	C compiler flags	"-O -g2", for example.
CPPFLAGS	C preprocessor options	"-DNDEBUG" to omit assertion checks, for example.
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.
ARFLAGS, NMFLAGS, FPP, M4FLAGS, LIBS, FLIBS, FLDFLAGS	Miscellaneous	One or more of these may be needed for some platforms. Unless required, you should not set these environment variables, because that may interfere with the configure script.

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