man/sd_journal_seek_head.xml

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<refentry id="sd_journal_seek_head">

        <refentryinfo>
                <title>sd_journal_seek_head</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_seek_head</refentrytitle>
                <manvolnum>3</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd_journal_seek_head</refname>
                <refname>sd_journal_seek_tail</refname>
                <refname>sd_journal_seek_monotonic_usec</refname>
                <refname>sd_journal_seek_realtime_usec</refname>
                <refname>sd_journal_seek_cursor</refname>
                <refpurpose>Seek to a position in the
                journal</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <funcsynopsis>
                        <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>

                        <funcprototype>
                                <funcdef>int <function>sd_journal_seek_head</function></funcdef>
                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_journal_seek_tail</function></funcdef>
                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_journal_seek_monotonic_usec</function></funcdef>
                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
                                <paramdef>sd_id128_t <parameter>boot_id</parameter></paramdef>
                                <paramdef>uint64_t <parameter>usec</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_journal_seek_realtime_usec</function></funcdef>
                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
                                <paramdef>uint64_t <parameter>usec</parameter></paramdef>
                        </funcprototype>

                        <funcprototype>
                                <funcdef>int <function>sd_journal_seek_cursor</function></funcdef>
                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
                                <paramdef>const char * <parameter>cursor</parameter></paramdef>
                        </funcprototype>
                </funcsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><function>sd_journal_seek_head()</function>
                seeks to the beginning of the journal, i.e. the oldest
                available entry.</para>

                <para>Similar,
                <function>sd_journal_seek_tail()</function> may be
                used to seek to the end of the journal, i.e. the most
                recent available entry.</para>

                <para><function>sd_journal_seek_monotonic_usec()</function>
                seeks to the entry with the specified monotonic
                timestamp, i.e. CLOCK_MONOOTONIC. Since monotonic time
                restarts on every reboot a boot ID needs to be
                specified as well.</para>

                <para><function>sd_journal_seek_realtime_usec()</function>
                seeks to the entry with the specified realtime
                (wallclock) timestamp, i.e. CLOCK_REALTIME. Note that
                the realtime clock is not necessary monotonic. If a
                realtime timestamp is ambiguous it is not defined
                which position is sought to.</para>

                <para><function>sd_journal_seek_cursor()</function>
                seeks to the entry located at the specified cursor
                string. For details on cursors see
                <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

                <para>Note that these calls do not actually make any
                entry the new current entry, this needs to be done in
                a separate step with a subsequent
                <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                invocation (or a similar call). Only then entry data
                may be retrieved via
                <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
                no entry exists that matches exactly the specified
                seek address the next closest is sought to. If
                <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                is used the closest following entry will be sought to,
                if
                <citerefentry><refentrytitle>sd_journal_previous</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                is used the closest preceding entry is sought
                to.</para>
        </refsect1>

        <refsect1>
                <title>Return Value</title>

                <para>The functions return 0 on success or a negative
                errno-style error code.</para>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>The <function>sd_journal_seek_head()</function>,
                <function>sd_journal_seek_tail()</function>,
                <function>sd_journal_seek_monotonic_usec()</function>,
                <function>sd_journal_seek_realtime_usec()</function>,
                and <function>sd_journal_seek_cursor()</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_open</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>,
                        <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>