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<html>
<head><title>
HDF5/H5 API Specification
</title></head>

<body bgcolor="#FFFFFF">


<hr>
<center>
<table border=0 width=98%>
<tr><td valign=top align=left>
<a href="H5.intro.html">Introduction to HDF5</a>&nbsp;<br>
<a href="H5.user.html">HDF5 User Guide</a>&nbsp;<br>
<a href="index.html">Other HDF5 documents and links</a>&nbsp;<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>&nbsp;&nbsp;
<br>
H5&nbsp;&nbsp;
<a href="RM_H5A.html">H5A</a>&nbsp;&nbsp;
<a href="RM_H5D.html">H5D</a>&nbsp;&nbsp;
<a href="RM_H5E.html">H5E</a>&nbsp;&nbsp;
<a href="RM_H5F.html">H5F</a>&nbsp;&nbsp;
<a href="RM_H5G.html">H5G</a>&nbsp;&nbsp;
<a href="RM_H5I.html">H5I</a>&nbsp;&nbsp;
<a href="RM_H5P.html">H5P</a>&nbsp;&nbsp;
<br>
<a href="RM_H5R.html">H5R</a>&nbsp;&nbsp;
<a href="RM_H5RA.html">H5RA</a>&nbsp;&nbsp;
<a href="RM_H5S.html">H5S</a>&nbsp;&nbsp;
<a href="RM_H5T.html">H5T</a>&nbsp;&nbsp;
<a href="RM_H5Z.html">H5Z</a>&nbsp;&nbsp;
<a href="Tools.html">Tools</a>&nbsp;&nbsp;
<a href="PredefDTypes.html">Datatypes</a>&nbsp;&nbsp;
</td></tr>
</table>
</center>
<hr>


<center>
<h1>H5: General Library Functions</h1>
</center>

These functions serve general-purpose needs of the HDF5 library
and it users.

<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>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td><td valign=top>
<ul>
    <li><a href="#Library-Version">H5get_libversion</a>
    <li><a href="#Library-VersCheck">H5check_version</a>
</ul>
</td><td>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</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>


<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.
</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 generall 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.
</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.
</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.
</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.
</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>
<dt><strong>Description:</strong>
    <dd><code>H5check_version</code> verifies that the arguments match the 
        version numbers compiled into the library.  This function is intended 
        to be called by the user to verify that the version of the header files 
        compiled into the application matches the version of the HDF5 library 
        being used.
        <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.
        <p>
        If the version numbers of the library do not match 
	the version numbers in the header files being checked, the library calls the
        standard C function <code>abort()</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.
</dl>


<hr>
<center>
<table border=0 width=98%>
<tr><td valign=top align=left>
<a href="H5.intro.html">Introduction to HDF5</a>&nbsp;<br>
<a href="H5.user.html">HDF5 User Guide</a>&nbsp;<br>
<a href="index.html">Other HDF5 documents and links</a>&nbsp;<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>&nbsp;&nbsp;
<br>
H5&nbsp;&nbsp;
<a href="RM_H5A.html">H5A</a>&nbsp;&nbsp;
<a href="RM_H5D.html">H5D</a>&nbsp;&nbsp;
<a href="RM_H5E.html">H5E</a>&nbsp;&nbsp;
<a href="RM_H5F.html">H5F</a>&nbsp;&nbsp;
<a href="RM_H5G.html">H5G</a>&nbsp;&nbsp;
<a href="RM_H5I.html">H5I</a>&nbsp;&nbsp;
<a href="RM_H5P.html">H5P</a>&nbsp;&nbsp;
<br>
<a href="RM_H5R.html">H5R</a>&nbsp;&nbsp;
<a href="RM_H5RA.html">H5RA</a>&nbsp;&nbsp;
<a href="RM_H5S.html">H5S</a>&nbsp;&nbsp;
<a href="RM_H5T.html">H5T</a>&nbsp;&nbsp;
<a href="RM_H5Z.html">H5Z</a>&nbsp;&nbsp;
<a href="Tools.html">Tools</a>&nbsp;&nbsp;
<a href="PredefDTypes.html">Datatypes</a>&nbsp;&nbsp;
</td></tr>
</table>
</center>
<hr>


<address>
<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a> 

<br>
Last modified:  17 July 2000

<br>
Describes HDF5 Release 1.4 Beta, December 2000


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