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<refentry id= "sd_journal_open" >
<refentryinfo >
<title > sd_journal_open</title>
<productname > systemd</productname>
<authorgroup >
<author >
<contrib > Developer</contrib>
<firstname > Lennart</firstname>
<surname > Poettering</surname>
<email > lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta >
<refentrytitle > sd_journal_open</refentrytitle>
<manvolnum > 3</manvolnum>
</refmeta>
<refnamediv >
<refname > sd_journal_open</refname>
<refname > sd_journal_open_directory</refname>
<refname > sd_journal_close</refname>
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<refname > sd_journal</refname>
<refname > SD_JOURNAL_LOCAL_ONLY</refname>
<refname > SD_JOURNAL_RUNTIME_ONLY</refname>
<refname > SD_JOURNAL_SYSTEM_ONLY</refname>
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<refpurpose > Open the system journal for reading</refpurpose>
</refnamediv>
<refsynopsisdiv >
<funcsynopsis >
<funcsynopsisinfo > #include < systemd/sd-journal.h> </funcsynopsisinfo>
<funcprototype >
<funcdef > int <function > sd_journal_open</function> </funcdef>
<paramdef > sd_journal** <parameter > ret</parameter> </paramdef>
<paramdef > int <parameter > flags</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > int <function > sd_journal_open_directory</function> </funcdef>
<paramdef > sd_journal** <parameter > ret</parameter> </paramdef>
<paramdef > const char* <parameter > path</parameter> </paramdef>
<paramdef > int <parameter > flags</parameter> </paramdef>
</funcprototype>
<funcprototype >
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<funcdef > void <function > sd_journal_close</function> </funcdef>
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<paramdef > sd_journal* <parameter > j</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 >
<title > Description</title>
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<para > <function > sd_journal_open()</function> opens
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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 <literal > sd_journal</literal> pointer, which on
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success will contain journal context object afterwards. The
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second argument is a flags field, which may consist of
the following flags ORed together:
<literal > SD_JOURNAL_LOCAL_ONLY</literal> makes sure
only journal files generated on the local machine will
be opened. <literal > SD_JOURNAL_RUNTIME_ONLY</literal>
makes sure only volatile journal files will be opened,
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excluding those which are stored on persistent
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storage. <literal > SD_JOURNAL_SYSTEM_ONLY</literal>
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will ensure that only journal files of system services
and the kernel (in opposition to user session processes) will
be opened.</para>
<para > <function > sd_journal_open_directory()</function>
is similar to <function > sd_journal_open()</function>
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.</para>
<para > <function > sd_journal_close()</function> will
close the journal context allocated with
<function > sd_journal_open()</function> or
<function > sd_journal_open_directory()</function> and
free its resources.</para>
<para > 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.</para>
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<para > See
<citerefentry > <refentrytitle > sd_journal_next</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
for an example how to iterate through the journal
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after opening it with
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<function > sd_journal_open()</function> .</para>
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<para > A journal context object returned by
<function > sd_journal_open()</function> references a
specific journal entry as <emphasis > current</emphasis> entry,
similar to a file seek index in a classic file system
file, but without absolute positions. It may be
altered with
<citerefentry > <refentrytitle > sd_journal_next</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
and
<citerefentry > <refentrytitle > sd_journal_seek_head</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
and related calls. The current entry position may be
exported in <emphasis > cursor</emphasis> strings, as accessible
via
<citerefentry > <refentrytitle > sd_journal_get_cursor</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> . 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)
<citerefentry > <refentrytitle > sd_journal_seek_cursor</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> .</para>
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<para > Notification of journal changes is available via
<function > sd_journal_get_fd()</function> and related
calls.</para>
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</refsect1>
<refsect1 >
<title > Return Value</title>
<para > The <function > sd_journal_open()</function> and
<function > sd_journal_open_directory()</function> calls
return 0 on success or a negative errno-style error
code. <function > sd_journal_close()</function> returns
nothing.</para>
</refsect1>
<refsect1 >
<title > Notes</title>
<para > The <function > sd_journal_open()</function> ,
<function > sd_journal_open_directory()</function> and
<function > sd_journal_close()</function> interfaces are
available as shared library, which can be compiled and
linked to with the
<literal > libsystemd-journal</literal>
<citerefentry > <refentrytitle > pkg-config</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry>
file.</para>
</refsect1>
<refsect1 >
<title > See Also</title>
<para >
<citerefentry > <refentrytitle > systemd</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd-journal</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_journal_next</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_journal_get_data</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
</para>
</refsect1>
</refentry>
