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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 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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