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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_journal_add_match</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 204</span><hr><div class="refentry"><a name="sd_journal_add_match"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_journal_add_match, sd_journal_add_disjunction, sd_journal_add_conjunction, sd_journal_flush_matches — Add or remove entry matches</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-journal.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_add_match</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>const void* <var class="pdparam">data</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">size</var><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_journal_add_disjunction</b>(</code></td><td>sd_journal* <var class="pdparam">j</var><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_journal_add_conjunction</b>(</code></td><td>sd_journal* <var class="pdparam">j</var><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">void <b class="fsfunc">sd_journal_flush_matches</b>(</code></td><td>sd_journal* <var class="pdparam">j</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm259780241840"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_journal_add_match()</code> adds
a match by which to filter the entries of the journal
file. Matches applied with this call will filter what
can be iterated through and read from the journal file
via calls like
<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
and
<a href="sd_journal_get_data.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_data</span>(3)</span></a>. Matches
are of the form <code class="literal">FIELD=value</code>, where
the field part is a short uppercase string consisting
only of 0-9, A-Z and the underscore. It may not begin
with two underscores or be the empty string. The value
part may be any value, including binary. If a match is
applied only entries with this field set will be
iterated. Multiple matches may be active at the same
time: if they apply to different fields only entries
with both fields set like this will be iterated, if
they apply to the same fields only entries where the
field takes one of the specified values will be
iterated. Well known fields are documented in
<a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>. Whenever
a new match is added the current entry position is
reset, and
<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a> (or a similar call)
needs to be called before entries can be read
again.</p><p><code class="function">sd_journal_add_disjunction()</code>
may be used to insert a disjunction (i.e. logical OR)
in the match list. If this call is invoked all
previously added matches since the last invocation of
<code class="function">sd_journal_add_disjunction()</code> or
<code class="function">sd_journal_add_conjunction()</code> are
combined in an OR with all matches added afterwards,
until
<code class="function">sd_journal_add_disjunction()</code> or
<code class="function">sd_journal_add_conjunction()</code> is
invoked again to begin the next OR or AND
term. </p><p><code class="function">sd_journal_add_conjunction()</code>
may be used to insert a conjunction (i.e. logical AND)
in the match list. If this call is invoked all
previously added matches since the last invocation of
<code class="function">sd_journal_add_conjunction()</code> are
combined in an AND with all matches added afterwards,
until
<code class="function">sd_journal_add_conjunction()</code> is
invoked again to begin the next AND term. The
combination of
<code class="function">sd_journal_add_match()</code>,
<code class="function">sd_journal_add_disjunction()</code> and
<code class="function">sd_journal_add_conjunction()</code> may
be used to build complex search terms, even though
full logical expressions are not available. Note that
<code class="function">sd_journal_add_conjunction()</code>
operates one level 'higher' than
<code class="function">sd_journal_add_disjunction()</code>. It
is hence possible to build an expression of AND terms,
consisting of OR terms, consisting of AND terms,
consisting of OR terms of matches (the latter OR
expression is implicitly created for matches with the
same field name, see above).</p><p><code class="function">sd_journal_flush_matches()</code>
may be used to flush all matches, disjunction and
conjunction terms again. After this call all filtering
is removed and all entries in the journal will be
iterated again.</p><p>Note that filtering via matches only applies to
the way the journal is read, it has no effect on storage
on disk.</p></div><div class="refsect1"><a name="idm259784119376"></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_journal_add_match()</code>,
<code class="function">sd_journal_add_disjunction()</code> and
<code class="function">sd_journal_add_conjunction()</code>
return 0 on success or a negative errno-style error
code. <code class="function">sd_journal_flush_matches()</code>
returns nothing.</p></div><div class="refsect1"><a name="idm259784115328"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The <code class="function">sd_journal_add_match()</code>,
<code class="function">sd_journal_add_disjunction()</code>,
<code class="function">sd_journal_add_conjunction()</code> and
<code class="function">sd_journal_flush_matches()</code>
interfaces are available as shared library, which can
be compiled and linked to with the
<code class="literal">libsystemd-journal</code>
<a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
file.</p></div><div class="refsect1"><a name="idm259784109488"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples">¶</a></h2><p>The following example adds matches to a journal
context object to iterate only through messages
generated by the Avahi service at the four error log
levels, plus all messages of the message ID
03bb1dab98ab4ecfbf6fff2738bdd964 coming from any
service (this example lacks the necessary error
checking):</p><pre class="programlisting">...
int add_matches(sd_journal *j) {
sd_journal_add_match(j, "_SYSTEMD_UNIT=avahi-daemon.service", 0);
sd_journal_add_match(j, "PRIORITY=0", 0);
sd_journal_add_match(j, "PRIORITY=1", 0);
sd_journal_add_match(j, "PRIORITY=2", 0);
sd_journal_add_match(j, "PRIORITY=3", 0);
sd_journal_add_disjunction(j);
sd_journal_add_match(j, "MESSAGE_ID=03bb1dab98ab4ecfbf6fff2738bdd964", 0);
}</pre></div><div class="refsect1"><a name="idm259784106784"></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-journal.html"><span class="citerefentry"><span class="refentrytitle">sd-journal</span>(3)</span></a>,
<a href="sd_journal_open.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_open</span>(3)</span></a>,
<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>,
<a href="sd_journal_get_data.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_data</span>(3)</span></a>,
<a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>
</p></div></div></body></html>
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