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<title>nsss: the nsss library interface</title>
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<p>
<a href="../">nsss</a><br />
<a href="//skarnet.org/software/">Software</a><br />
<a href="//skarnet.org/">skarnet.org</a>
</p>
<h1> The <tt>nsss</tt> library interface </h1>
<h2> General information </h2>
<p>
<tt>libnsss</tt> is a client library meant to be used by client
programs needing utmp functionality. It interacts with various
server-side daemons such as
<a href="../nsssd-unix.html">nsssd-unix</a>.
</p>
<p>
Application programs can use it directly, but most existing programs
simply use the standard
<a href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/pwd.h.html">pwd.h</a>,
<a href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/grp.h.html">grp.h</a> or
<a href="http://man7.org/linux/man-pages/man3/getspnam.3.html">shadow.h</a>
interfaces, which in nsss are implemented as a series of thin wrappers
around the nsss library.
</p>
<h2> Compiling </h2>
<ul>
<li> Make sure the nsss headers, as well as the skalibs headers,
are visible in your header search path. </li>
<li> Use <tt>#include <nsss/nsss.h></tt> </li>
<li> To use the standard <tt>pwd.h</tt> interface, you can
just <tt>#include <pwd.h></tt>, which will work as long
as the <tt>nsss/pwd.h</tt> header is accessible in your header
search path. </li>
<li> Same thing for <tt>grp.h</tt> and <tt>shadow.h</tt>. </li>
</ul>
<h2> Linking </h2>
<ul>
<li> Make sure the nsss library, as well as the skalibs library,
are visible in your library search path. </li>
<li> Link against <tt>-lnsss</tt>, <tt>-lskarnet</tt>, </li>
<tt>`cat $SYSDEPS/socket.lib`</tt> and
<tt>`cat $SYSDEPS/tainnow.lib`</tt>, $SYSDEPS being your skalibs
sysdeps directory. </li>
</ul>
<h2> Programming </h2>
<p>
The <tt>nsss/nsss.h</tt> header is actually a collection of headers:
</p>
<ul>
<li> <tt>nsss/nsss-unix.h</tt> implements basic access to the
<tt>/etc/passwd</tt>, <tt>/etc/group</tt> and <tt>/etc/shadow</tt>
database. </li>
<li> <tt>nsss/nsss-switch.h</tt> implements connection via a Unix
domain socket to a listening <tt>nsssd</tt> daemon, implementing an
authentication backend based on what implementation of
the daemon is listening. </li>
<li> <tt>nsss/nsss-all.h</tt> implements a safe policy: first a
connection via <tt>nsss-switch</tt> is attempted, and if no daemon
is listening, the safe <tt>nsss-unix</tt> backend is used. </li>
</ul>
<p>
By default, the <tt>getpwnam()</tt> et al. functions are aliased
to their <tt>nsss-all</tt> implementations. You can disable the
<tt>nsss-unix</tt> fallback by compiling with the NSSS_DISABLE_UNIX
macro defined (-DNSSS_DISABLE_UNIX). Or you can disable any
attempt to connect to a daemon by compiling with the
NSSS_DISABLE_SWITCH macro defined (-DNSSS_DISABLE_SWITCH).
</p>
<p>
(To be completed.)
</p>
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