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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_journal_open</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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</style><a href="index.html">Index </a>·
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 208</span><hr><div class="refentry"><a name="sd_journal_open"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_journal_open, sd_journal_open_directory, sd_journal_open_files, sd_journal_close, sd_journal, SD_JOURNAL_LOCAL_ONLY, SD_JOURNAL_RUNTIME_ONLY, SD_JOURNAL_SYSTEM, SD_JOURNAL_CURRENT_USER — Open the system journal for reading</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_open</b>(</code></td><td>sd_journal** <var class="pdparam">ret</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</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_open_directory</b>(</code></td><td>sd_journal** <var class="pdparam">ret</var>, </td></tr><tr><td> </td><td>const char* <var class="pdparam">path</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</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_open_files</b>(</code></td><td>sd_journal** <var class="pdparam">ret</var>, </td></tr><tr><td> </td><td>const char** <var class="pdparam">paths</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">flags</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_close</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="idm274677924448"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_journal_open()</code> opens
the log journal for reading. It will find all journal
files automatically and interleave them automatically
when reading. As first argument it takes a pointer to
a <code class="varname">sd_journal</code> pointer, which on
success will contain a journal context object. The
second argument is a flags field, which may consist of
the following flags ORed together:
<code class="constant">SD_JOURNAL_LOCAL_ONLY</code> makes sure
only journal files generated on the local machine will
be opened. <code class="constant">SD_JOURNAL_RUNTIME_ONLY</code>
makes sure only volatile journal files will be opened,
excluding those which are stored on persistent
storage. <code class="constant">SD_JOURNAL_SYSTEM</code>
will cause journal files of system services and the
kernel (in opposition to user session processes) to
be opened. <code class="constant">SD_JOURNAL_CURRENT_USER</code>
will cause journal files of the current user to be
opened. If neither <code class="constant">SD_JOURNAL_SYSTEM</code>
nor <code class="constant">SD_JOURNAL_CURRENT_USER</code> are
specified, all journal file types will be opened.</p><p><code class="function">sd_journal_open_directory()</code>
is similar to <code class="function">sd_journal_open()</code>
but takes an absolute directory path as argument. All
journal files in this directory will be opened and
interleaved automatically. This call also takes a
flags argument, but it must be passed as 0 as no flags
are currently understood for this call.</p><p><code class="function">sd_journal_open_files()</code>
is similar to <code class="function">sd_journal_open()</code>
but takes a <code class="constant">NULL</code>-terminated list
of file paths to open. All files will be opened and
interleaved automatically. This call also takes a
flags argument, but it must be passed as 0 as no flags
are currently understood for this call. Please note
that in the case of a live journal, this function is only
useful for debugging, because individual journal files
can be rotated at any moment, and the opening of
specific files is inherently racy.</p><p><code class="varname">sd_journal</code> objects cannot be
used in the child after a fork. Functions which take a
journal object as an argument
(<code class="function">sd_journal_next()</code> and others)
will return <code class="constant">-ECHILD</code> after a fork.
</p><p><code class="function">sd_journal_close()</code> will
close the journal context allocated with
<code class="function">sd_journal_open()</code> or
<code class="function">sd_journal_open_directory()</code> and
free its resources.</p><p>When opening the journal only journal files
accessible to the calling user will be opened. If
journal files are not accessible to the caller, this
will be silently ignored.</p><p>See
<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
for an example of how to iterate through the journal
after opening it with
<code class="function">sd_journal_open()</code>.</p><p>A journal context object returned by
<code class="function">sd_journal_open()</code> references a
specific journal entry as <span class="emphasis"><em>current</em></span> entry,
similar to a file seek index in a classic file system
file, but without absolute positions. It may be
altered with
<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
and
<a href="sd_journal_seek_head.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_seek_head</span>(3)</span></a>
and related calls. The current entry position may be
exported in <span class="emphasis"><em>cursor</em></span> strings, as accessible
via
<a href="sd_journal_get_cursor.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_cursor</span>(3)</span></a>. Cursor
strings may be used to globally identify a specific
journal entry in a stable way and then later to seek
to it (or if the specific entry is not available
locally, to its closest entry in time)
<a href="sd_journal_seek_cursor.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_seek_cursor</span>(3)</span></a>.</p><p>Notification of journal changes is available via
<code class="function">sd_journal_get_fd()</code> and related
calls.</p></div><div class="refsect1"><a name="idm274677893168"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>The <code class="function">sd_journal_open()</code>,
<code class="function">sd_journal_open_directory()</code>, and
<code class="function">sd_journal_open_files()</code> calls
return 0 on success or a negative errno-style error
code. <code class="function">sd_journal_close()</code> returns
nothing.</p></div><div class="refsect1"><a name="idm274677888960"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The <code class="function">sd_journal_open()</code>,
<code class="function">sd_journal_open_directory()</code> and
<code class="function">sd_journal_close()</code> interfaces are
available as a shared library, which can be compiled and
linked to with the
<code class="constant">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="idm274677884112"></a><h2 id="History">History<a class="headerlink" title="Permalink to this headline" href="#History">¶</a></h2><p><code class="function">sd_journal_open()</code>,
<code class="function">sd_journal_close()</code>,
<code class="constant">SD_JOURNAL_LOCAL_ONLY</code>,
<code class="constant">SD_JOURNAL_RUNTIME_ONLY</code>,
<code class="constant">SD_JOURNAL_SYSTEM_ONLY</code> were added
in systemd-38.</p><p><code class="function">sd_journal_open_directory()</code>
was added in systemd-187.</p><p><code class="constant">SD_JOURNAL_SYSTEM</code>,
<code class="constant">SD_JOURNAL_CURRENT_USER</code>,
and <code class="function">sd_journal_open_files()</code>
were added in systemd-205.
<code class="constant">SD_JOURNAL_SYSTEM_ONLY</code>
was deprecated.</p></div><div class="refsect1"><a name="idm274672909856"></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_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>
</p></div></div></body></html>
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