Ncview++

Ncview++ is a from-scratch C++/FLTK/CMake port of ncview, David W. Pierce's netCDF visual browser. The original is C + X11/Xt/Athena widgets built with autotools; this port replaces the toolkit with FLTK and the build with CMake. FLTK and UDUNITS-2 are vendored as git submodules and built from source, so there's no separate FLTK/ UDUNITS-2 install step -- see Prerequisites below for what those submodule builds and the rest of the project actually need on the build machine (netCDF and expat as libraries; flex, bison, and texinfo as build tools).

See CHANGELOG.md for what's changed release-to-release, and docs/PORTING.md for the porting plan and design rationale.

Names

The command is ncview++, and it installs its colormaps and man page under ncview++ names, so it can be installed alongside the original ncview. Where + isn't allowed or safe (the GitHub repository, release archives, the CMake project name) the name is spelled ncviewpp. Settings are still kept in ~/.ncviewrc, and extra colormaps are still found via $NCVIEWBASE, same as with the original.

License

GNU General Public License, version 3 -- see LICENSE. Ncview itself is Copyright (C) 1993 through 2024, David W. Pierce; Ncview++ is Copyright (C) 2026 Dominik Strebel.

Installing

Pre-built packages for Linux, macOS, and Windows are on the Releases page.

Building from source

Prerequisites: a C++17 compiler, CMake >= 3.21, netCDF (C library + headers), expat, and — on Linux/BSD — X11 dev headers (libx11-dev libxext-dev libxft-dev libxinerama-dev libxcursor-dev libxrender-dev libxfixes-dev on Debian/Ubuntu). FLTK and UDUNITS-2 are built from the vendored submodules, but the vendored UDUNITS-2 build itself needs flex, bison, and texinfo on the build machine (on Unix it unconditionally regenerates its lexer/parser from source with flex/ bison, and generates its documentation with texinfo's makeinfo/ install-info) — flex bison texinfo on Debian/Ubuntu.

git submodule update --init --recursive
cmake -S . -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo
cmake --build build -j
ctest --test-dir build

./build/app/ncview++ some_file.nc

To install:

cmake --install build --prefix /usr/local

This bundles every non-system shared library the binary needs (netCDF, HDF5, X11, ...) alongside it, so the install (or the .tar.gz/.zip from cmake --build build --target package) is self-contained. Always pass --prefix explicitly — the default resolves to this repo's parent directory, a quirk of the vendored UDUNITS-2 build.

Static linking (HPC clusters etc.)

-DNCVIEW_STATIC_LINK=ON statically links netCDF/HDF5/zstd/bz2/sz/zlib and the C++ runtime, and drops FLTK's Wayland backend (unused at runtime, but otherwise pulls in ~80 transitive shared libraries). Requires static (.a) builds of those libraries to be findable. See docs/PORTING.md for what's deliberately left dynamic and why.

cmake -S . -B build-static -DCMAKE_BUILD_TYPE=RelWithDebInfo -DNCVIEW_STATIC_LINK=ON
cmake --build build-static -j
ldd build-static/app/ncview++   # confirm netcdf/hdf5 are no longer listed

Releasing

Tag a commit vX.Y.Z and push the tag — .github/workflows/release.yml builds all three platforms and publishes the archives to a GitHub Release. Keep the tag in sync with CPACK_PACKAGE_VERSION in the top-level CMakeLists.txt.

git tag v0.4.0
git push origin v0.4.0

To re-publish an existing tag (e.g. after a CI flake), run release.yml manually from the Actions tab with that tag name.

---

Note: after configuring, you may see root-level README, COPYRIGHT, and CHANGE_LOG files (no .md suffix) appear. Those are UDUNITS-2's own files, generated there at configure time (from its own copies) because its vendored CMake build hardcodes those paths at the repo root -- not tracked, not this project's own files.