# HDF5 Library **URL:** https://forum.hdfgroup.org/c/hdf5/8.md [Latest](https://forum.hdfgroup.org/latest.md) · [Categories](https://forum.hdfgroup.org/categories.md) --- ## [\[OBSOLETE\] HDF5 Working Group meeting](https://forum.hdfgroup.org/t/obsolete-hdf5-working-group-meeting/12282)
**Author:** [@derobins](https://forum.hdfgroup.org/u/derobins)\ **Replies:** 3\ **Last updated:** [July 1, 2026, 5:36pm UTC](https://forum.hdfgroup.org/t/obsolete-hdf5-working-group-meeting/12282 "2026-07-01T17:36:54Z")
The HDF5 Working Group meets weekly, on Thursdays at 10 am Central time. This meeting is for HDF5 library developers and anyone is welcome to attend. The purpose of this meeting is to discuss HDF5 library development. It… --- ## [Read Before Posting: Welcome to The HDF Forum](https://forum.hdfgroup.org/t/read-before-posting-welcome-to-the-hdf-forum/10930)
**Author:** [@lori.cooper](https://forum.hdfgroup.org/u/lori.cooper)\ **Replies:** 0\ **Last updated:** [March 14, 2023, 3:12pm UTC](https://forum.hdfgroup.org/t/read-before-posting-welcome-to-the-hdf-forum/10930 "2023-03-14T15:12:33Z")
Welcome to The HDF Forum. This forum is maintained by The HDF Group, the developers and maintainers of HDF technologies. It is a community-driven forum first, and HDF Group staff will help find answers to questions on a … --- ## [About the HDF5 Library category](https://forum.hdfgroup.org/t/about-the-hdf5-library-category/21)
**Author:** [@lori.cooper](https://forum.hdfgroup.org/u/lori.cooper)\ **Replies:** 0\ **Last updated:** [February 7, 2018, 11:11pm UTC](https://forum.hdfgroup.org/t/about-the-hdf5-library-category/21 "2018-02-07T23:11:55Z")
All HDF5 Library questions. --- ## [Concurrent read while writing HDF5 file (without SWMR): intermittent metadata / object header errors — any supported workaround?](https://forum.hdfgroup.org/t/concurrent-read-while-writing-hdf5-file-without-swmr-intermittent-metadata-object-header-errors-any-supported-workaround/13659)
**Author:** [@younesr008](https://forum.hdfgroup.org/u/younesr008)\ **Replies:** 2\ **Last updated:** [August 19, 2026, 11:41pm UTC](https://forum.hdfgroup.org/t/concurrent-read-while-writing-hdf5-file-without-swmr-intermittent-metadata-object-header-errors-any-supported-workaround/13659 "2026-08-19T23:41:02Z")
Hello I am trying to read an HDF5 file while it is being written by another process, without using SWMR mode. I understand that this may not be officially supported, but I would like to understand whether there is any s… --- ## [Build tests failing on HDF5-2.2.0 for aarch64](https://forum.hdfgroup.org/t/build-tests-failing-on-hdf5-2-2-0-for-aarch64/13863)
**Author:** [@lwilbert](https://forum.hdfgroup.org/u/lwilbert)\ **Replies:** 1\ **Last updated:** [August 7, 2026, 5:29pm UTC](https://forum.hdfgroup.org/t/build-tests-failing-on-hdf5-2-2-0-for-aarch64/13863 "2026-08-07T17:29:12Z")
I’m attempting to build hdf5-2.2.0 on aarch64 Ubuntu 24.04.4, but the build fails when running some of the tests. What I’ve done: Downloaded the .tar.gz from Github (hdf5-2.2.0.tar.gz) As root, untarred into a directo… --- ## [New vs Old Documentation URLs](https://forum.hdfgroup.org/t/new-vs-old-documentation-urls/9802)
**Author:** [@kittisopikulm](https://forum.hdfgroup.org/u/kittisopikulm)\ **Replies:** 10\ **Last updated:** [July 17, 2026, 9:14pm UTC](https://forum.hdfgroup.org/t/new-vs-old-documentation-urls/9802 "2026-07-17T21:14:33Z")
The portal.hdgroup.org URLs have a nice feature in that they encode the name of the function n the URL: https://portal.hdfgroup.org/display/HDF5/H5D\_CLOSE The new docs.hdfgroup.org URLs use numbered “title” anchors. h… --- ## [C++ equivalence of Python code for HDF5. Working with datasets resizing, working with indexes \[i\]\[j\] in array-like structures, etc](https://forum.hdfgroup.org/t/c-equivalence-of-python-code-for-hdf5-working-with-datasets-resizing-working-with-indexes-i-j-in-array-like-structures-etc/13836)
**Author:** [@mlt.2](https://forum.hdfgroup.org/u/mlt.2)\ **Replies:** 8\ **Last updated:** [June 22, 2026, 9:16pm UTC](https://forum.hdfgroup.org/t/c-equivalence-of-python-code-for-hdf5-working-with-datasets-resizing-working-with-indexes-i-j-in-array-like-structures-etc/13836 "2026-06-22T21:16:30Z")
This post is about code conversion from Python to C++ about HDF5, trying to keep the C++ part simplified, and this about a specific part from a previous post here, just in order to separate that whole content in separate… --- ## [Use C preprocessor macros (e.g. version numbers) in Fortran](https://forum.hdfgroup.org/t/use-c-preprocessor-macros-e-g-version-numbers-in-fortran/7298)
**Author:** [@jonathan.schilling](https://forum.hdfgroup.org/u/jonathan.schilling)\ **Replies:** 6\ **Last updated:** [June 19, 2026, 2:16pm UTC](https://forum.hdfgroup.org/t/use-c-preprocessor-macros-e-g-version-numbers-in-fortran/7298 "2026-06-19T14:16:22Z")
Hi there, I am currently working on a Fortran codebase, which uses HDF5 as output file format. The code runs on various machines, from laptops to supercomputers (hence many different compilers, versions of HDF5 etc.). T… --- ## [Hdf5 on Rust as a Cargo crate](https://forum.hdfgroup.org/t/hdf5-on-rust-as-a-cargo-crate/12725)
**Author:** [@lrossi](https://forum.hdfgroup.org/u/lrossi)\ **Replies:** 12\ **Last updated:** [June 18, 2026, 2:14pm UTC](https://forum.hdfgroup.org/t/hdf5-on-rust-as-a-cargo-crate/12725 "2026-06-18T14:14:47Z")
Hi all, I would really love to use hdf5 in my rust codebase but I’m a bit concerned. the most used wrapper that I know of is this one: hdf5 - Rust but it is not getting updates (does not even work with the latest vers… --- ## [C++ equivalence of Python code for HDF5. Is possible to write 2d std::vector to HDF5 file similarly to 2d std::array? or more simplified in general](https://forum.hdfgroup.org/t/c-equivalence-of-python-code-for-hdf5-is-possible-to-write-2d-std-vector-to-hdf5-file-similarly-to-2d-std-array-or-more-simplified-in-general/13832)
**Author:** [@mlt.2](https://forum.hdfgroup.org/u/mlt.2)\ **Replies:** 4\ **Last updated:** [June 16, 2026, 5:12pm UTC](https://forum.hdfgroup.org/t/c-equivalence-of-python-code-for-hdf5-is-possible-to-write-2d-std-vector-to-hdf5-file-similarly-to-2d-std-array-or-more-simplified-in-general/13832 "2026-06-16T17:12:56Z")
This post is about code conversion from Python to C++ about HDF5, trying to keep the C++ part simplified. General process in the program about HDF5: Generate a .h5 file with one or more datasets. Writing/reading if th… --- ## [Unable to make HDF5 and HDFView work, both at the same time, neither with the .msi HDF5 installation nor with the vcpkg HDF5 installation](https://forum.hdfgroup.org/t/unable-to-make-hdf5-and-hdfview-work-both-at-the-same-time-neither-with-the-msi-hdf5-installation-nor-with-the-vcpkg-hdf5-installation/13824)
**Author:** [@mlt.2](https://forum.hdfgroup.org/u/mlt.2)\ **Replies:** 4\ **Last updated:** [June 15, 2026, 7:23pm UTC](https://forum.hdfgroup.org/t/unable-to-make-hdf5-and-hdfview-work-both-at-the-same-time-neither-with-the-msi-hdf5-installation-nor-with-the-vcpkg-hdf5-installation/13824 "2026-06-15T19:23:56Z")
I’m trying to work with HDF5 in a cpp program and at the same time also with HDFView (v3.4.1, currently the most recent version). I’m new with HDF5 and currently I’m trying to work with the next program example: h5tutr… --- ## [Explainer on outcome of "page\_buf\_size" value](https://forum.hdfgroup.org/t/explainer-on-outcome-of-page-buf-size-value/13809)
**Author:** [@carroll.ian](https://forum.hdfgroup.org/u/carroll.ian)\ **Replies:** 3\ **Last updated:** [June 8, 2026, 2:19pm UTC](https://forum.hdfgroup.org/t/explainer-on-outcome-of-page-buf-size-value/13809 "2026-06-08T14:19:16Z")
The h5py.File argument page\_buf\_size is confusing me, and since there’s a lot of enthusiasm for cloud-optimization of HDF5 files, I thought asking for a brief public explainer would be useful. The docs say the value “mu… --- ## [Need clarification of how to read variable length strings in C code](https://forum.hdfgroup.org/t/need-clarification-of-how-to-read-variable-length-strings-in-c-code/13814)
**Author:** [@shawn.fox](https://forum.hdfgroup.org/u/shawn.fox)\ **Replies:** 1\ **Last updated:** [June 3, 2026, 12:01pm UTC](https://forum.hdfgroup.org/t/need-clarification-of-how-to-read-variable-length-strings-in-c-code/13814 "2026-06-03T12:01:40Z")
Looking at the H5Dread API, it isn’t clear to me whether the caller should allocate the memory of the buffer. It only shows one example for a data type of integer and the caller does create the memory buffer before makin… --- ## [Building HDF5 with Fortran](https://forum.hdfgroup.org/t/building-hdf5-with-fortran/13802)
**Author:** [@mikez](https://forum.hdfgroup.org/u/mikez)\ **Replies:** 1\ **Last updated:** [June 2, 2026, 2:35pm UTC](https://forum.hdfgroup.org/t/building-hdf5-with-fortran/13802 "2026-06-02T14:35:09Z")
Trying to build HDF5 libraries with Fortran support for VASP using Intel MPI. It doesn’t seem to be creating the .mod files even though I’m using -DHDF5\_BUILD\_FORTRAN:BOOL=ON in CMAKE. tried using .tgz and git source c… --- ## [HDF5 binary difference](https://forum.hdfgroup.org/t/hdf5-binary-difference/13709)
**Author:** [@julie](https://forum.hdfgroup.org/u/julie)\ **Replies:** 14\ **Last updated:** [May 29, 2026, 5:42pm UTC](https://forum.hdfgroup.org/t/hdf5-binary-difference/13709 "2026-05-29T17:42:22Z")
I created a conversion application for a client using the HDF5 libraries. This application was working fine for them as of late 2024. I made some updates in 2025. It worked well on my desktop and I was able to convert th… --- ## [RFC: Internal Multithreading for Chunk I/O](https://forum.hdfgroup.org/t/rfc-internal-multithreading-for-chunk-i-o/13808)
**Author:** [@nfortne2](https://forum.hdfgroup.org/u/nfortne2)\ **Replies:** 0\ **Last updated:** [May 28, 2026, 9:11pm UTC](https://forum.hdfgroup.org/t/rfc-internal-multithreading-for-chunk-i-o/13808 "2026-05-28T21:11:49Z")
Here is an RFC describing a new feature we’re developing that will accelerate chunked I/O by internally splitting the operation into multiple threads, with each thread handling one chunk (or more than one if there are mo… --- ## [Filter plugin maintainers: confirm a canonical name for your filter](https://forum.hdfgroup.org/t/filter-plugin-maintainers-confirm-a-canonical-name-for-your-filter/13797)
**Author:** [@brtnfld](https://forum.hdfgroup.org/u/brtnfld)\ **Replies:** 0\ **Last updated:** [May 15, 2026, 6:45pm UTC](https://forum.hdfgroup.org/t/filter-plugin-maintainers-confirm-a-canonical-name-for-your-filter/13797 "2026-05-15T18:45:36Z")
If you maintain a registered HDF5 filter plugin, we’d like a few minutes of your time. What’s changing. HDF5 2.x introduces a new filter plugin class, H5Z\_class3\_t, that adds a string-based configuration API for filters… --- ## [How to properly close HDF files when disk is full?](https://forum.hdfgroup.org/t/how-to-properly-close-hdf-files-when-disk-is-full/11714)
**Author:** [@andreas.beckmann](https://forum.hdfgroup.org/u/andreas.beckmann)\ **Replies:** 13\ **Last updated:** [May 12, 2026, 2:14pm UTC](https://forum.hdfgroup.org/t/how-to-properly-close-hdf-files-when-disk-is-full/11714 "2026-05-12T14:14:02Z")
If a disk becomes full while writing datasets, you get an OSError with errno 28, which is expected. However, h5py.File.close() also throws an OSError exception. If you terminate the application, you get further OSErrors … --- ## [Proposal: shape-aware filter plugins for HDF5 (cross-codec preprocessor with measured wins)](https://forum.hdfgroup.org/t/proposal-shape-aware-filter-plugins-for-hdf5-cross-codec-preprocessor-with-measured-wins/13782)
**Author:** [@rjamesy](https://forum.hdfgroup.org/u/rjamesy)\ **Replies:** 1\ **Last updated:** [May 5, 2026, 4:12pm UTC](https://forum.hdfgroup.org/t/proposal-shape-aware-filter-plugins-for-hdf5-cross-codec-preprocessor-with-measured-wins/13782 "2026-05-05T16:12:26Z")
\## Question: would STRATA-style shape-aware filters be useful as HDF5 plugins? Hi all, I have built a small MIT-licensed lossless preprocessing library called \*\*STRATA\*\*: https://github.com/rjamesy/strata STRATA expo… --- ## [RFC-HDFG-2026-001: String-Based Filter Configuration API — Request for Community Feedback](https://forum.hdfgroup.org/t/rfc-hdfg-2026-001-string-based-filter-configuration-api-request-for-community-feedback/13776)
**Author:** [@brtnfld](https://forum.hdfgroup.org/u/brtnfld)\ **Replies:** 1\ **Last updated:** [May 1, 2026, 10:46pm UTC](https://forum.hdfgroup.org/t/rfc-hdfg-2026-001-string-based-filter-configuration-api-request-for-community-feedback/13776 "2026-05-01T22:46:38Z")
Hi all, We are seeking community feedback on a new RFC proposing a unified, string-based filter configuration interface for HDF5. The current H5Pset\_filter interface requires filter parameters to be passed as raw unsig… --- ## [How to know version numbers at compile time (Fortran)](https://forum.hdfgroup.org/t/how-to-know-version-numbers-at-compile-time-fortran/13772)
**Author:** [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\ **Replies:** 1\ **Last updated:** [April 27, 2026, 5:15am UTC](https://forum.hdfgroup.org/t/how-to-know-version-numbers-at-compile-time-fortran/13772 "2026-04-27T05:15:10Z")
Hi all… How can I get the library’s version numbers for preprocessing in Fortran? An AI taught me a lie; I cannot find hdf5.inc in hdf5-{1.14,2.0.0,2.1.0}… Thanks in advance. --- ## [Where can I download the files mentioned in "Improving I/O Performance...":?](https://forum.hdfgroup.org/t/where-can-i-download-the-files-mentioned-in-improving-i-o-performance/13768)
**Author:** [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\ **Replies:** 5\ **Last updated:** [April 22, 2026, 10:50pm UTC](https://forum.hdfgroup.org/t/where-can-i-download-the-files-mentioned-in-improving-i-o-performance/13768 "2026-04-22T22:50:36Z")
Hi, Where can I download the files mentioned as “\[ 7 \]” We will use two HDF5 files to compare I/O performance and to illustrate the issues users may encounter when working with compressed data. These HDF5 files and th… --- ## [Checking about corruption issues with hdf5 core driver](https://forum.hdfgroup.org/t/checking-about-corruption-issues-with-hdf5-core-driver/13738)
**Author:** [@swapnilojha](https://forum.hdfgroup.org/u/swapnilojha)\ **Replies:** 4\ **Last updated:** [April 16, 2026, 3:01pm UTC](https://forum.hdfgroup.org/t/checking-about-corruption-issues-with-hdf5-core-driver/13738 "2026-04-16T15:01:19Z")
I am writing some string data(S75) to datasets and using core driver with lzf compression. I am using python with h5py 3.15 and hdf5 2.0.0. Occasionally, what I have seen is that the chunk in the h5 file overwrites anot… --- ## [Typical format using HDF5+XDMF to save a AMR](https://forum.hdfgroup.org/t/typical-format-using-hdf5-xdmf-to-save-a-amr/13755)
**Author:** [@dreamerking](https://forum.hdfgroup.org/u/dreamerking)\ **Replies:** 6\ **Last updated:** [April 14, 2026, 1:31am UTC](https://forum.hdfgroup.org/t/typical-format-using-hdf5-xdmf-to-save-a-amr/13755 "2026-04-14T01:31:46Z")
Hi there,all! I’m new to HDF5, and am working on an AMR generator recently. I want to use HDF5+XDMF to save the AMR as an .h5 and an .xdmf file. The structure of my AMR is like this: The mesh has N block, and each bl… --- ## [H5repack and GZIP - Version 1.14.6 vs 2.1](https://forum.hdfgroup.org/t/h5repack-and-gzip-version-1-14-6-vs-2-1/13747)
**Author:** [@tobias.holzmann](https://forum.hdfgroup.org/u/tobias.holzmann)\ **Replies:** 6\ **Last updated:** [April 10, 2026, 2:11pm UTC](https://forum.hdfgroup.org/t/h5repack-and-gzip-version-1-14-6-vs-2-1/13747 "2026-04-10T14:11:35Z")
Hey all, I found some strange behavior of h5repack which I don´t understand in detail. We are using OpenFOAM for CFD simulations and recently the vtkhdf writer was funded. For that we compiled OpenFOAM with HDF5 version … --- ## [Is there any way to recover possibly corrupted SWMR files?](https://forum.hdfgroup.org/t/is-there-any-way-to-recover-possibly-corrupted-swmr-files/13631)
**Author:** [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\ **Replies:** 9\ **Last updated:** [April 6, 2026, 4:44pm UTC](https://forum.hdfgroup.org/t/is-there-any-way-to-recover-possibly-corrupted-swmr-files/13631 "2026-04-06T16:44:34Z")
Dear experts… I submitted a job to a PBS-professional managed queue on our supercomputer. The job is a Monte-Carlo calculation done using MPI and OpenMP and the obtained data are stored with HDF-2.0.0 library (SWMR): n… --- ## [The number of bytes used for "Page Bits" in Extensible Array Indexing Information](https://forum.hdfgroup.org/t/the-number-of-bytes-used-for-page-bits-in-extensible-array-indexing-information/13725)
**Author:** [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\ **Replies:** 4\ **Last updated:** [March 27, 2026, 4:01pm UTC](https://forum.hdfgroup.org/t/the-number-of-bytes-used-for-page-bits-in-extensible-array-indexing-information/13725 "2026-03-27T16:01:42Z")
Does the “Page Bits” in Extensible Array Indexing Information really use two bytes? --- ## [System installed zlib not being used when building HDF5 2.0 with cmake](https://forum.hdfgroup.org/t/system-installed-zlib-not-being-used-when-building-hdf5-2-0-with-cmake/13701)
**Author:** [@joseph.kelmer](https://forum.hdfgroup.org/u/joseph.kelmer)\ **Replies:** 10\ **Last updated:** [February 18, 2026, 11:15pm UTC](https://forum.hdfgroup.org/t/system-installed-zlib-not-being-used-when-building-hdf5-2-0-with-cmake/13701 "2026-02-18T23:15:30Z")
I am working on building hdf5-2.0.0 on a rhel8 system. It currently has zlib-1.2.11 installed. Reading through the instructions in the INSTALL\_Cmake.txt file, specifically: If you plan to use Zlib or Szip (aka libaec)… --- ## [Advice on storing many datasets in parallel ?](https://forum.hdfgroup.org/t/advice-on-storing-many-datasets-in-parallel/13692)
**Author:** [@mimc](https://forum.hdfgroup.org/u/mimc)\ **Replies:** 7\ **Last updated:** [February 9, 2026, 10:21pm UTC](https://forum.hdfgroup.org/t/advice-on-storing-many-datasets-in-parallel/13692 "2026-02-09T22:21:50Z")
Hello Folks, I have a MPI cluster workflow that generate millions of small datasets in parallel. So far I have it programed where all the worker ranks, send these small datasets to rank-0, where it is written to an HDF5… --- ## [Threads::Threads linked unconditionally to hdf5::hdf5-static and hdf5::hdf5\_fortran-static](https://forum.hdfgroup.org/t/threads-threads-linked-unconditionally-to-hdf5-hdf5-static-and-hdf5-hdf5-fortran-static/13641)
**Author:** [@furutaka.kazuyoshi](https://forum.hdfgroup.org/u/furutaka.kazuyoshi)\ **Replies:** 2\ **Last updated:** [February 5, 2026, 6:21pm UTC](https://forum.hdfgroup.org/t/threads-threads-linked-unconditionally-to-hdf5-hdf5-static-and-hdf5-hdf5-fortran-static/13641 "2026-02-05T18:21:08Z")
Dear experts… In cmake/hdf5-targets.cmake of the 2.0.0 library, Threads::Threads seems to be linked to hdf5::hdf5-static and hdf5::hdf5\_fortran-static regardless of the setting on wheather to use threading or not, bu… [Next page](https://forum.hdfgroup.org/c/hdf5/8.md?page=1)