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<h4 class="subsection">28.3.1 The Naming Scheme of the NSS Modules</h4>

<p class="noindent">The name of each function consist of various parts:

   <blockquote>
       _nss_<var>service</var>_<var>function</var>
</blockquote>

   <p><var>service</var> of course corresponds to the name of the module this
function is found in.<a rel="footnote" href="#fn-1" name="fnd-1"><sup>1</sup></a>  The <var>function</var> part is derived
from the interface function in the C library itself.  If the user calls
the function <code>gethostbyname</code> and the service used is <code>files</code>
the function

<pre class="smallexample">            _nss_files_gethostbyname_r
</pre>
   <p class="noindent">in the module

<pre class="smallexample">            libnss_files.so.2
</pre>
   <p class="noindent"><a name="index-reentrant-NSS-functions-3285"></a>is used.  You see, what is explained above in not the whole truth.  In
fact the NSS modules only contain reentrant versions of the lookup
functions.  I.e., if the user would call the <code>gethostbyname_r</code>
function this also would end in the above function.  For all user
interface functions the C library maps this call to a call to the
reentrant function.  For reentrant functions this is trivial since the
interface is (nearly) the same.  For the non-reentrant version The
library keeps internal buffers which are used to replace the user
supplied buffer.

   <p>I.e., the reentrant functions <em>can</em> have counterparts.  No service
module is forced to have functions for all databases and all kinds to
access them.  If a function is not available it is simply treated as if
the function would return <code>unavail</code>
(see <a href="Actions-in-the-NSS-configuration.html#Actions-in-the-NSS-configuration">Actions in the NSS configuration</a>).

   <p>The file name <samp><span class="file">libnss_files.so.2</span></samp> would be on a Solaris&nbsp;2<!-- /@w -->
system <samp><span class="file">nss_files.so.2</span></samp>.  This is the difference mentioned above. 
Sun's NSS modules are usable as modules which get indirectly loaded
only.

   <p>The NSS modules in the GNU C Library are prepared to be used as normal
libraries themselves.  This is <em>not</em> true at the moment, though. 
However,  the organization of the name space in the modules does not make it
impossible like it is for Solaris.  Now you can see why the modules are
still libraries.<a rel="footnote" href="#fn-2" name="fnd-2"><sup>2</sup></a>

   <div class="footnote">
<hr>
<h4>Footnotes</h4><p class="footnote"><small>[<a name="fn-1" href="#fnd-1">1</a>]</small> Now you might ask why this information is
duplicated.  The answer is that we want to make it possible to link
directly with these shared objects.</p>

   <p class="footnote"><small>[<a name="fn-2" href="#fnd-2">2</a>]</small> There is a second explanation: we were too
lazy to change the Makefiles to allow the generation of shared objects
not starting with <samp><span class="file">lib</span></samp> but don't tell this to anybody.</p>

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