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<html>
<head><title>
HDF5/H5 API Specification
</title>
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<a href="index.html">HDF5 documents and links</a> <br>
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And in this document, the
<a href="RM_H5Front.html">HDF5 Reference Manual</a>
<br>
<a href="RM_H5.html">H5</a>
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<!-- #EndLibraryItem --><center>
<h1>H5: General Library Functions</h1>
</center>
These functions serve general-purpose needs of the HDF5 library
and it users.
<p>
<strong>The C Interfaces:</strong>
<table border=0>
<tr><td valign=top>
<ul>
<li><a href="#Library-Open">H5open</a>
<li><a href="#Library-Close">H5close</a>
</ul>
</td><td> </td><td valign=top>
<ul>
<li><a href="#Library-Version">H5get_libversion</a>
<li><a href="#Library-VersCheck">H5check_version</a>
</ul>
</td><td> </td><td valign=top>
<ul>
<li><a href="#Library-GarbageCollect">H5garbage_collect</a>
<li><a href="#Library-DontAtExit">H5dont_atexit</a>
</ul>
</td></tr>
</table>
<p>
<strong>The FORTRAN90 Interfaces:</strong>
<br>
<font size=-1>
<i>In general, each FORTRAN90 subroutine performs exactly the same task
as the corresponding C function. The links below go to the C function
descriptions, which serve as general descriptions for both. A button,
under <strong>Non-C API(s)</strong> at the end of the C function description,
opens an external browser window displaying the FORTRAN90-specific
information. You will probably want to adjust the size and location of
this external window so that both browser windows are visible and to
facilitate moving easily between them.</i>
</font>
<table border=0>
<tr><td valign=top>
<ul>
<li><a href="#Library-Open">h5open_f</a>
<li><a href="#Library-Close">h5close_f</a>
</ul>
</td><td> </td><td valign=top>
<ul>
<li><a href="#Library-Version">h5get_libversion_f</a>
<li><a href="#Library-VersCheck">h5check_version_f</a>
</ul>
</td><td> </td><td valign=top>
<ul>
<li><a href="#Library-GarbageCollect">h5garbage_collect_f</a>
<li><a href="#Library-DontAtExit">h5dont_atexit_f</a>
</ul>
</td></tr>
</table>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Library-Open">H5open</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5open</code>(<em>void</em>)
<dt><strong>Purpose:</strong>
<dd>Initializes the HDF5 library.
<dt><strong>Description:</strong>
<dd><code>H5open</code> initialize the library. This function is
normally called automatically, but if you find that an
HDF5 library function is failing inexplicably, try calling
this function first.
<dt><strong>Parameters:</strong>
<dl>
<dt>None.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a non-negative value if successful;
otherwise returns a negative value.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5_FORTRAN.html#h5open_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Library-Close">H5close</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5close</code>(<em>void</em>)
<dt><strong>Purpose:</strong>
<dd>Flushes all data to disk, closes file identifiers, and cleans up memory.
<dt><strong>Description:</strong>
<dd><code>H5close</code> flushes all data to disk,
closes all file identifiers, and cleans up all memory used by
the library. This function is generally called when the
application calls <code>exit</code>, but may be called earlier
in event of an emergency shutdown or out of desire to free all
resources used by the HDF5 library.
<dt><strong>Parameters:</strong>
<dl>
<dt>None.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a non-negative value if successful;
otherwise returns a negative value.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5_FORTRAN.html#h5close_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Library-GarbageCollect">H5garbage_collect</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5garbage_collect</code>(<em>void</em>)
<dt><strong>Purpose:</strong>
<dd>Garbage collects on all free-lists of all types.
<dt><strong>Description:</strong>
<dd><code>H5garbage_collect</code> walks through all the garbage
collection routines of the library, freeing any unused memory.
<p>
It is not required that <code>H5garbage_collect</code> be called
at any particular time; it is only necessary in certain situations
where the application has performed actions that cause the library
to allocate many objects. The application should call
<code>H5garbage_collect</code> if it eventually releases those
objects and wants to reduce the memory used by the library from
the peak usage required.
<p>
The library automatically garbage collects all the free lists
when the application ends.
<dt><strong>Parameters:</strong>
<dl>
<dt>None.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a non-negative value if successful;
otherwise returns a negative value.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5_FORTRAN.html#h5garbage_collect_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Library-DontAtExit">H5dont_atexit</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5dont_atexit</code>(<em>void</em>)
<dt><strong>Purpose:</strong>
<dd>Instructs library not to install <code>atexit</code> cleanup routine.
<dt><strong>Description:</strong>
<dd><code>H5dont_atexit</code> indicates to the library that an
<code>atexit()</code> cleanup routine should not be installed.
The major purpose for this is in situations where the
library is dynamically linked into an application and is
un-linked from the application before <code>exit()</code> gets
called. In those situations, a routine installed with
<code>atexit()</code> would jump to a routine which was
no longer in memory, causing errors.
<p>
In order to be effective, this routine <em>must</em> be called
before any other HDF function calls, and must be called each
time the library is loaded/linked into the application
(the first time and after it's been un-loaded).
<dt><strong>Parameters:</strong>
<dl>
<dt>None.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a non-negative value if successful;
otherwise returns a negative value.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5_FORTRAN.html#h5dont_atexit_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Library-Version">H5get_libversion</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5get_libversion</code>(<em>unsigned *</em><code>majnum</code>,
<em>unsigned *</em><code>minnum</code>,
<em>unsigned *</em><code>relnum</code>
)
<dt><strong>Purpose:</strong>
<dd>Returns the HDF library release number.
<dt><strong>Description:</strong>
<dd><code>H5get_libversion</code> retrieves the major, minor, and release
numbers of the version of the HDF library which is linked to
the application.
<dt><strong>Parameters:</strong>
<dl>
<dt><em>unsigned *</em><code>majnum</code>
<dd>OUT: The major version of the library.
<dt><em>unsigned *</em><code>minnum</code>
<dd>OUT: The minor version of the library.
<dt><em>unsigned *</em><code>relnum</code>
<dd>OUT: The release number of the library.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a non-negative value if successful;
otherwise returns a negative value.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5_FORTRAN.html#h5get_libversion_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<hr>
<dl>
<dt><strong>Name:</strong> <a name="Library-VersCheck">H5check_version</a>
<dt><strong>Signature:</strong>
<dd><em>herr_t</em> <code>H5check_version</code>(<em>unsigned</em> <code>majnum</code>,
<em>unsigned</em> <code>minnum</code>,
<em>unsigned</em> <code>relnum</code>
)
<dt><strong>Purpose:</strong>
<dd>Verifies that library versions are consistent.
<dt><strong>Description:</strong>
<dd><code>H5check_version</code> verifies that the arguments provided
with the function call match the version numbers compiled into
the library.
<p>
<code>H5check_version</code> serves two slightly differing purposes.
<p>
First, the function is intended to be called by the user to verify
that the version of the header files compiled into an application
matches the version of the HDF5 library being used.
One may look at the <code>H5check</code> definition in the file
<code>H5public.h</code> as an example.
<p>
Due to the risks of data corruption or segmentation faults,
<code>H5check_version</code> causes the application to abort if the
version numbers do not match.
The abort is achieved by means of a call to the
standard C function <code>abort()</code>.
<p>
Note that <code>H5check_version</code> verifies only the
major and minor version numbers and the release number;
it does not verify the sub-release value as that should be
an empty string for any official release.
This means that any two incompatible library versions must
have different {major,minor,release} numbers. (Notice the
reverse is not necessarily true.)
<p>
Secondarily, <code>H5check_version</code> verifies that the
library version identifiers <code>H5_VERS_MAJOR</code>,
<code>H5_VERS_MINOR</code>, <code>H5_VERS_RELEASE</code>,
<code>H5_VERS_SUBRELEASE</code>, and <code>H5_VERS_INFO</code>
are consistent.
This is designed to catch source code inconsistencies,
but does not generate the fatal error as in the first stage
because this inconsistency does not cause errors in the data files.
If this check reveals inconsistencies, the library issues a warning
but the function does not fail.
<!--
<p>
<strong><em>Alternate to preceding paragraph / More to the point?</em></strong>
<br>
If the function passes the above test and does not generate
an <code>abort()</code> call, the function's second purpose
comes into play.
<code>H5check_version</code> then procedes to verify
that the additional library version identifiers
<code>H5_VERS_SUBRELEASE</code>, and <code>H5_VERS_INFO</code>
are consistent.
This is designed to catch source code inconsistencies,
but does not generate the fatal error
that is generated under the first function.
<p>
The version and release numbers passed as
<code>H5check_version</code> parameters have the
following relationsips to each other:
<dir>
An official HDF5 release is labelled as
<br>
HDF5 Release <<code>majnum</code>><strong>.</strong><<code>minnum</code>><strong>.</strong><<code>relnum</code>>
</dir>
For example, in the version of the library known as HDF5 Release 1.4.2,
the 1 is the major version number, <code>majnum</code>;
the 1 is the minor version number, <code>minnum</code>; and
the 1 is the release number, <code>relnum</code>.
-->
<dt><strong>Parameters:</strong>
<dl>
<dt><em>unsigned </em><code>majnum</code>
<dd>IN: The major version of the library.
<dt><em>unsigned </em><code>minnum</code>
<dd>IN: The minor version of the library.
<dt><em>unsigned </em><code>relnum</code>
<dd>IN: The release number of the library.
</dl>
<dt><strong>Returns:</strong>
<dd>Returns a non-negative value if successful.
Upon failure, this function causes the application to abort.
<dt><strong>Non-C API(s):</strong>
<dd><a href="fortran/h5_FORTRAN.html#h5check_version_f"
target="FortranWin"><img src="Graphics/FORTRAN.gif" border=0></a>
<!--
<img src="Graphics/Java.gif">
<img src="Graphics/C++.gif">
-->
</dl>
<!-- #BeginLibraryItem "/ed_libs/NavBar_RM.lbi" --><hr>
<center>
<table border=0 width=98%>
<tr><td valign=top align=left>
<a href="index.html">HDF5 documents and links</a> <br>
<a href="H5.intro.html">Introduction to HDF5</a> <br>
<a href="H5.user.html">HDF5 User Guide</a> <br>
<!--
<a href="Glossary.html">Glossary</a><br>
-->
</td>
<td valign=top align=right>
And in this document, the
<a href="RM_H5Front.html">HDF5 Reference Manual</a>
<br>
<a href="RM_H5.html">H5</a>
<a href="RM_H5A.html">H5A</a>
<a href="RM_H5D.html">H5D</a>
<a href="RM_H5E.html">H5E</a>
<a href="RM_H5F.html">H5F</a>
<a href="RM_H5G.html">H5G</a>
<a href="RM_H5I.html">H5I</a>
<a href="RM_H5P.html">H5P</a>
<br>
<a href="RM_H5R.html">H5R</a>
<a href="RM_H5S.html">H5S</a>
<a href="RM_H5T.html">H5T</a>
<a href="RM_H5Z.html">H5Z</a>
<a href="Tools.html">Tools</a>
<a href="PredefDTypes.html">Datatypes</a>
</td></tr>
</table>
</center>
<hr>
<!-- #EndLibraryItem --><!-- #BeginLibraryItem "/ed_libs/Footer.lbi" --><address>
<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
<br>
Describes HDF5 Release 1.5, Unreleased Development Branch
</address><!-- #EndLibraryItem -->
Last modified: 3 April 2003
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