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<div><div class="header">
  <div class="headertitle"><div class="title">Discovering the Contents of an HDF5 File</div></div>
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<div class="contents">
<div class="textblock"><p>Navigate back: <a class="el" href="index.html">Main</a> / <a class="el" href="_getting_started.html">Getting Started with HDF5</a> / <a class="el" href="_learn_basics.html">Learning the Basics</a> </p><hr  />
<h1><a class="anchor" id="secLBContents"></a>
Discovering what is in an HDF5 file</h1>
<p>HDFView and <a class="el" href="_h5_t_o_o_l__d_p__u_g.html#sec_cltools_h5dump">h5dump</a> are standalone tools which cannot be called within an application, and using <a class="el" href="_h5version_8h.html#a7dba2e5b2045f31c0932123ffb54f7a3">H5Dopen</a> and <a class="el" href="group___h5_d.html#ga8287d5a7be7b8e55ffeff68f7d26811c" title="Reads raw data from a dataset into a provided buffer.">H5Dread</a> require that you know the name of the HDF5 dataset. How would an application that has no prior knowledge of an HDF5 file be able to determine or discover the contents of it, much like HDFView and <a class="el" href="_h5_t_o_o_l__d_p__u_g.html#sec_cltools_h5dump">h5dump</a>?</p>
<p>The answer is that there are ways to discover the contents of an HDF5 file, by using the <a class="el" href="group___h5_g.html">Groups (H5G)</a>, <a class="el" href="group___h5_l.html">Links (H5L)</a> and <a class="el" href="group___h5_o.html">Objects (H5O)</a> APIs: </p><ul>
<li>The <a class="el" href="group___h5_g.html">Groups (H5G)</a> interface (covered earlier) consists of routines for working with groups. A group is a structure that can be used to organize zero or more HDF5 objects, not unlike a Unix directory. </li>
<li>The <a class="el" href="group___h5_l.html">Links (H5L)</a> interface consists of link routines. A link is a path between groups. The <a class="el" href="group___h5_l.html">Links (H5L)</a> interface allows objects to be accessed by use of these links. </li>
<li>The <a class="el" href="group___h5_o.html">Objects (H5O)</a> interface consists of routines for working with objects. Datasets, groups, and committed datatypes are all objects in HDF5.</li>
</ul>
<p>Interface routines that simplify the process: </p><ul>
<li><a class="el" href="group___t_r_a_v.html#ga55406698106930db68242987c11ba051">H5Literate</a> traverses the links in a specified group, in the order of the specified index, using a user-defined callback routine. (A callback function is one that will be called when a certain condition is met, at a certain point in the future.) </li>
<li><a class="el" href="group___h5_o.html#ga5ce86255fcc34ceaf84a62551cd24233">H5Ovisit</a> / <a class="el" href="group___t_r_a_v.html#gac0558936502924d9e898d8b6e041ed69">H5Lvisit</a> recursively visit all objects/links accessible from a specified object/group.</li>
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<h1><a class="anchor" id="secLBContentsProg"></a>
Programming Example</h1>
<h2><a class="anchor" id="subsecLBContentsProgUsing"></a>
Using H5Literate, H5Lvisit and H5Ovisit</h2>
<p>For example code, see the <a class="el" href="_h_d_f5_examples.html">HDF5 Examples</a> page. Specifically look at the <a class="el" href="_ex_a_p_i.html">Examples by API</a>. There are examples for different languages, where examples of using <a class="el" href="group___t_r_a_v.html#ga55406698106930db68242987c11ba051">H5Literate</a> and <a class="el" href="group___h5_o.html#ga5ce86255fcc34ceaf84a62551cd24233">H5Ovisit</a>/<a class="el" href="group___t_r_a_v.html#gac0558936502924d9e898d8b6e041ed69">H5Lvisit</a> are included.</p>
<p>The h5ex_g_traverse example traverses a file using H5Literate: </p><ul>
<li>C: <a href="https://github.com/HDFGroup/hdf5/blob/develop/HDF5Examples/C/H5G/h5ex_g_traverse.c">h5ex_g_traverse.c</a> </li>
<li>F90: <a href="https://github.com/HDFGroup/hdf5/blob/develop/HDF5Examples/FORTRAN/H5G/h5ex_g_traverse.F90">h5ex_g_traverse_F03.f90</a></li>
</ul>
<p>The h5ex_g_visit example traverses a file using H5Ovisit and H5Lvisit: </p><ul>
<li>C: <a href="https://github.com/HDFGroup/hdf5/blob/develop/HDF5Examples/C/H5G/h5ex_g_visit.c">h5ex_g_visit.c</a> </li>
<li>F90: <a href="https://github.com/HDFGroup/hdf5/blob/develop/HDF5Examples/FORTRAN/H5G/h5ex_g_visit.F90">h5ex_g_visit_F03.f90</a></li>
</ul>
<hr  />
<p> Previous Chapter <a class="el" href="_l_b_com_dset.html">Compressed Datasets</a> - Next Chapter <a class="el" href="_l_b_quiz.html">Learning the basics QUIZ</a></p>
<p>Navigate back: <a class="el" href="index.html">Main</a> / <a class="el" href="_getting_started.html">Getting Started with HDF5</a> / <a class="el" href="_learn_basics.html">Learning the Basics</a> </p>
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