Installation

Prerequisites

A Fortran 2008 compiler is required:

Compiler	Version
GNU gfortran	12 or newer (tested 12, 13, 14, 16); gfortran 11 builds, but the string form of vtm_file%write_block crashes
Intel Fortran (ifx)	tested with 2025.3 (the fobos Intel modes run ifx; the discontinued ifort is not tested)

Download

Clone the repository, then fetch its third-party dependencies with FoBiS.py (they are listed in the [dependencies] section of fobos):

git clone https://github.com/szaghi/VTKFortran
cd VTKFortran
pip install FoBiS.py
fobis fetch

CMake and FoBiS.py builds need the fetched dependencies; fpm fetches its own (see fpm.toml). The release assets include an install.sh script that downloads a release, fetches the dependencies and builds it (install.sh --help).

Third-Party Dependencies

fobis fetch places them under src/third_party/:

Library	Purpose
PENF	Portable numeric kind parameters (I4P, R8P, etc.) — used everywhere
BeFoR64	Base64 encode/decode for binary XML data
StringiFor	OOP string type used throughout the writer classes
FoXy	XML tags emitting (the writers; the readers have their own scanner)
FACE	ANSI terminal colour output

Build with CMake (preferred)

CMake is the recommended build system for library use and integration into other projects.

cmake -S . -B build
cmake --build build

Run the test suite

cmake -S . -B build -DBUILD_TESTING=ON
cmake --build build
ctest --test-dir build

Run a single named test:

ctest --test-dir build -R vtk_fortran_write_vtu --output-on-failure

Each test program prints Are all tests passed? T (or F) and exits with a non-zero status when a check fails. CTest runs each test in its own directory, build/src/tests/run/<test name>/, where its VTK files are left for inspection; the executables are in build/src/tests/.

CMake subdirectory integration

To embed VTKFortran in an existing CMake project, place a clone (with its dependencies fetched) alongside your sources and add to your CMakeLists.txt:

add_subdirectory(VTKFortran)

target_link_libraries(your_target VTKFortran::VTKFortran)

Build with FoBiS.py

FoBiS.py (CLI fobis) is also used for coverage analysis and documentation generation.

List all build modes

fobis build --lmodes

Build and run tests

fobis build --mode tests-gnu
scripts/run_tests.sh

Compiled test executables are placed in ./exe/. scripts/run_tests.sh runs each executable and reports pass/fail from its exit status (it runs them in the current directory, where they write their VTK files).

Build the library

# Static library (GNU gfortran)
fobis build --mode static-gnu

# Shared library (GNU gfortran)
fobis build --mode shared-gnu

# Intel Fortran variants
fobis build --mode static-intel
fobis build --mode shared-intel

Debug builds

fobis build --mode static-gnu-debug
fobis build --mode tests-gnu-debug   # with zlib, as the CI

Coverage and documentation

fobis rule --ex makecoverage   # build + run tests + gcov report
fobis rule --ex makedoc        # build the API reference (formal) and the VitePress site (needs formal and npm)

makecoverage calls scripts/compute-coverage.sh, which automatically selects the gcov-N binary that matches the installed gfortran version. If you run the script directly, ensure that gfortran is on $PATH so the version is detected correctly.

Build with FPM

fpm build --profile release

fpm 0.13.0 or newer is required (fpm.toml uses the [features] table). fpm builds the library (and fetches its dependencies); the test programs are built with CMake or FoBiS.py.

Optional zlib compression

The compression of binary data (compressor='zlib', format='raw-zlib', see Compressed binary data) needs zlib and the preprocessor macro VTKFORTRAN_USE_ZLIB at build time. Without it the library builds and works as usual, and requesting zlib makes initialize return a non-zero error. Install the zlib development files first (e.g. apt install zlib1g-dev).

CMake: enable the option; zlib is found with find_package(ZLIB).

cmake -S . -B build -DVTKFORTRAN_USE_ZLIB=ON
cmake --build build

FoBiS.py: the tests-gnu-debug mode (the CI one) is built with zlib. For other modes, or your own fobos, add -DVTKFORTRAN_USE_ZLIB to cflags and link zlib with ext_libs = z.

fpm: pass the macro and link zlib. With GNU ld, --no-as-needed is needed because zlib is listed before the library that uses it:

fpm build --flag "-DVTKFORTRAN_USE_ZLIB" --link-flag "-Wl,--no-as-needed -lz"