systemd/man/sd_id128_to_string.html
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</span><hr><div class="refentry"><a name="sd_id128_to_string"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_id128_to_string, sd_id128_from_string — Format or parse 128-bit IDs as strings</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include &lt;systemd/sd-id128.h&gt;</pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">char *<b class="fsfunc">sd_id128_to_string</b>(</code></td><td>sd_id128_t <var class="pdparam">id</var>, char <var class="pdparam">s</var>[33]<code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_id128_from_string</b>(</code></td><td>const char *<var class="pdparam">s</var>, sd_id128_t *<var class="pdparam">ret</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm140369556398160"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description"></a></h2><p><code class="function">sd_id128_to_string()</code> formats a 128-bit
ID as a character string. It expects the ID and a string array
capable of storing 33 characters. The ID will be formatted as 32
lowercase hexadecimal digits and be terminated by a
<code class="constant">NUL</code> byte.</p><p><code class="function">sd_id128_from_string()</code> implements the
reverse operation: it takes a 33 character string with 32
hexadecimal digits (either lowercase or uppercase, terminated by
<code class="constant">NUL</code>) and parses them back into a 128-bit ID
returned in <em class="parameter"><code>ret</code></em>. Alternatively, this call
can also parse a 37-character string with a 128-bit ID formatted
as RFC UUID.</p><p>For more information about the "<code class="literal">sd_id128_t</code>"
type see
<a href="sd-id128.html"><span class="citerefentry"><span class="refentrytitle">sd-id128</span>(3)</span></a>.
Note that these calls operate the same way on all architectures,
i.e. the results do not depend on endianness.</p><p>When formatting a 128-bit ID into a string, it is often
easier to use a format string for
<a href="http://man7.org/linux/man-pages/man3/printf.3.html"><span class="citerefentry"><span class="refentrytitle">printf</span>(3)</span></a>.
This is easily done using the
<code class="function">SD_ID128_FORMAT_STR</code> and
<code class="function">SD_ID128_FORMAT_VAL()</code> macros. For more
information see
<a href="sd-id128.html"><span class="citerefentry"><span class="refentrytitle">sd-id128</span>(3)</span></a>.</p></div><div class="refsect1"><a name="idm140369560290192"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value"></a></h2><p><code class="function">sd_id128_to_string()</code> always succeeds
and returns a pointer to the string array passed in.
<code class="function">sd_id128_from_string</code> returns 0 on success, in
which case <em class="parameter"><code>ret</code></em> is filled in, or a negative
errno-style error code.</p></div><div class="refsect1"><a name="idm140369560287104"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes"></a></h2><p>The <code class="function">sd_id128_to_string()</code> and
<code class="function">sd_id128_from_string()</code> interfaces are
available as a shared library, which can be compiled and linked to
with the
"<code class="literal">libsystemd</code>" <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
file.</p></div><div class="refsect1"><a name="idm140369560282528"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also"></a></h2><p>
<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
<a href="sd-id128.html"><span class="citerefentry"><span class="refentrytitle">sd-id128</span>(3)</span></a>,
<a href="http://man7.org/linux/man-pages/man3/printf.3.html"><span class="citerefentry"><span class="refentrytitle">printf</span>(3)</span></a>
</p></div></div></body></html>