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man: clarify that sd_journal_seek_head() seeks *before* the first entry

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Lennart Poettering 2019-03-13 12:29:25 +01:00 committed by Zbigniew Jędrzejewski-Szmek
parent a3b1790c1a
commit 88f739cb11
1 changed files with 24 additions and 32 deletions
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56
man/sd_journal_seek_head.xml
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@ -66,46 +66,38 @@
<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><function>sd_journal_seek_head()</function> seeks to the beginning of the journal, i.e. to the
position before the oldest available entry.</para>
<para>Similarly, <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>Similarly, <function>sd_journal_seek_tail()</function> may be used to seek to the end of the
journal, i.e. the position after 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.
<constant>CLOCK_MONOTONIC</constant>. Since monotonic time
restarts on every reboot a boot ID needs to be specified as
well.</para>
<para><function>sd_journal_seek_monotonic_usec()</function> seeks to a position with the specified
monotonic timestamp, i.e. <constant>CLOCK_MONOTONIC</constant>. 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. <constant>CLOCK_REALTIME</constant>. Note that the realtime
clock is not necessarily monotonic. If a realtime timestamp is
ambiguous, it is not defined which position is sought to.</para>
<para><function>sd_journal_seek_realtime_usec()</function> seeks to a position with the specified
realtime (wallclock) timestamp, i.e. <constant>CLOCK_REALTIME</constant>. Note that the realtime clock is
not necessarily 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
<para><function>sd_journal_seek_cursor()</function> seeks to the position at the specified cursor
string. For details on cursors, see
<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
If no entry matching the specified cursor is found the call will
seek to the next closest entry (in terms of time) instead. To
verify whether the newly selected entry actually matches the
cursor, use
If no entry matching the specified cursor is found the call will seek to the next closest entry (in terms
of time) instead. To verify whether the newly selected entry actually matches the cursor, use
<citerefentry><refentrytitle>sd_journal_test_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
<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
invocation (or a similar call). Only then, entry data may be retrieved via
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
or an entry cursor be retrieved via
<citerefentry><refentrytitle>sd_journal_get_cursor</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>