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man: update docs with the new functions and other enhancements
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
parent
7cbb7d62c6
commit
0da322d9a4
@ -18,6 +18,7 @@
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<refnamediv>
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<refname>sd_journal_get_data</refname>
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<refname>sd_journal_enumerate_data</refname>
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<refname>sd_journal_enumerate_available_data</refname>
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<refname>sd_journal_restart_data</refname>
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<refname>SD_JOURNAL_FOREACH_DATA</refname>
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<refname>sd_journal_set_data_threshold</refname>
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@ -44,6 +45,13 @@
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<paramdef>size_t *<parameter>length</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_enumerate_available_data</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>const void **<parameter>data</parameter></paramdef>
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<paramdef>size_t *<parameter>length</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_journal_restart_data</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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@ -73,24 +81,18 @@
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<refsect1>
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<title>Description</title>
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<para><function>sd_journal_get_data()</function> gets the data
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object associated with a specific field from the current journal
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entry. It takes four arguments: the journal context object, a
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string with the field name to request, plus a pair of pointers to
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pointer/size variables where the data object and its size shall be
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stored in. The field name should be an entry field name.
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Well-known field names are listed in
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
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The returned data is in a read-only memory map and is only valid
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until the next invocation of
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<function>sd_journal_get_data()</function> or
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<function>sd_journal_enumerate_data()</function>, or the read
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pointer is altered. Note that the data returned will be prefixed
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with the field name and '='. Also note that, by default, data fields
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larger than 64K might get truncated to 64K. This threshold may be
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changed and turned off with
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<function>sd_journal_set_data_threshold()</function> (see
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below).</para>
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<para><function>sd_journal_get_data()</function> gets the data object associated with a specific field
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from the current journal entry. It takes four arguments: the journal context object, a string with the
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field name to request, plus a pair of pointers to pointer/size variables where the data object and its
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size shall be stored in. The field name should be an entry field name. Well-known field names are listed in
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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but any field can be specified. The returned data is in a read-only memory map and is only valid until
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the next invocation of <function>sd_journal_get_data()</function>,
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<function>sd_journal_enumerate_data()</function>,
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<function>sd_journal_enumerate_available_data()</function>, or when the read pointer is altered. Note
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that the data returned will be prefixed with the field name and <literal>=</literal>. Also note that, by
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default, data fields larger than 64K might get truncated to 64K. This threshold may be changed and turned
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off with <function>sd_journal_set_data_threshold()</function> (see below).</para>
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<para><function>sd_journal_enumerate_data()</function> may be used
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to iterate through all fields of the current entry. On each
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@ -99,15 +101,18 @@
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format as with <function>sd_journal_get_data()</function> and also
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follows the same life-time semantics.</para>
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<para><function>sd_journal_enumerate_available_data()</function> is similar to
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<function>sd_journal_enumerate_data()</function>, but silently skips any fields which may be valid, but
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are too large or not supported by current implementation.</para>
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<para><function>sd_journal_restart_data()</function> resets the
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data enumeration index to the beginning of the entry. The next
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invocation of <function>sd_journal_enumerate_data()</function>
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will return the first field of the entry again.</para>
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<para>Note that the <function>SD_JOURNAL_FOREACH_DATA()</function>
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macro may be used as a handy wrapper around
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<function>sd_journal_restart_data()</function> and
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<function>sd_journal_enumerate_data()</function>.</para>
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<para>Note that the <function>SD_JOURNAL_FOREACH_DATA()</function> macro may be used as a handy wrapper
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around <function>sd_journal_restart_data()</function> and
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<function>sd_journal_enumerate_available_data()</function>.</para>
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<para>Note that these functions will not work before
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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@ -139,18 +144,88 @@
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<refsect1>
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<title>Return Value</title>
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<para><function>sd_journal_get_data()</function> returns 0 on
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success or a negative errno-style error code. If the current entry
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does not include the specified field, -ENOENT is returned. If
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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has not been called at least once, -EADDRNOTAVAIL is returned.
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<function>sd_journal_enumerate_data()</function> returns a
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positive integer if the next field has been read, 0 when no more
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fields are known, or a negative errno-style error code.
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<function>sd_journal_restart_data()</function> returns nothing.
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<function>sd_journal_set_data_threshold()</function> and
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<function>sd_journal_get_threshold()</function> return 0 on
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success or a negative errno-style error code.</para>
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<para><function>sd_journal_get_data()</function> returns 0 on success or a negative errno-style error
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code. <function>sd_journal_enumerate_data()</function> and
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<function>sd_journal_enumerate_available_data()</function> return a positive integer if the next field
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has been read, 0 when no more fields remain, or a negative errno-style error code.
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<function>sd_journal_restart_data()</function> doesn't return anything.
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<function>sd_journal_set_data_threshold()</function> and <function>sd_journal_get_threshold()</function>
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return 0 on success or a negative errno-style error code.</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry id='EINVAL'>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>One of the required parameters is <constant>NULL</constant> or invalid.
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</para></listitem>
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</varlistentry>
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<varlistentry id='ECHILD'>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The journal object was created in a different process.</para></listitem>
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</varlistentry>
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<varlistentry id='EADDRNOTAVAIL'>
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<term><constant>-EADDRNOTAVAIL</constant></term>
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<listitem><para>The read pointer is not positioned at a valid entry;
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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or a related call has not been called at least once.</para></listitem>
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</varlistentry>
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<varlistentry id='ENOENT'>
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<term><constant>-ENOENT</constant></term>
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<listitem><para>The current entry does not include the specified field.</para>
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</listitem>
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</varlistentry>
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<varlistentry id='ENOMEM'>
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<term><constant>-ENOMEM</constant></term>
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<listitem><para>Memory allocation failed.</para></listitem>
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</varlistentry>
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<varlistentry id='ENOBUFS'>
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<term><constant>-ENOBUFS</constant></term>
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<listitem><para>A compressed entry is too large.</para></listitem>
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</varlistentry>
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<varlistentry id='E2BIG'>
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<term><constant>-E2BIG</constant></term>
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<listitem><para>The data field is too large for this computer architecture (e.g. above 4 GB on a
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32-bit architecture).</para></listitem>
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</varlistentry>
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<varlistentry id='EPROTONOSUPPORT'>
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<term><constant>-EPROTONOSUPPORT</constant></term>
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<listitem><para>The journal is compressed with an unsupported method or the journal uses an
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unsupported feature.</para></listitem>
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</varlistentry>
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<varlistentry id='EBADMSG'>
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<term><constant>-EBADMSG</constant></term>
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<listitem><para>The journal is corrupted (possibly just the entry being iterated over).
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</para></listitem>
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</varlistentry>
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<varlistentry id='EIO'>
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<term><constant>-EIO</constant></term>
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<listitem><para>An I/O error was reported by the kernel.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<refsect1>
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@ -18,6 +18,7 @@
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<refnamediv>
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<refname>sd_journal_query_unique</refname>
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<refname>sd_journal_enumerate_unique</refname>
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<refname>sd_journal_enumerate_available_unique</refname>
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<refname>sd_journal_restart_unique</refname>
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<refname>SD_JOURNAL_FOREACH_UNIQUE</refname>
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<refpurpose>Read unique data fields from the journal</refpurpose>
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@ -33,6 +34,13 @@
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<paramdef>const char *<parameter>field</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_enumerate_available_unique</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>const void **<parameter>data</parameter></paramdef>
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<paramdef>size_t *<parameter>length</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_enumerate_unique</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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@ -58,33 +66,31 @@
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<refsect1>
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<title>Description</title>
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<para><function>sd_journal_query_unique()</function> queries the
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journal for all unique values the specified field can take. It
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takes two arguments: the journal to query and the field name to
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look for. Well-known field names are listed on
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
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Field names must be specified without a trailing '='. After this
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function has been executed successfully the field values may be
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queried using <function>sd_journal_enumerate_unique()</function>.
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Invoking this call a second time will change the field name being
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queried and reset the enumeration index to the first field value
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that matches.</para>
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<para><function>sd_journal_query_unique()</function> queries the journal for all unique values the
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specified field can take. It takes two arguments: the journal to query and the field name to look
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for. Well-known field names are listed on
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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but any field can be specified. Field names must be specified without a trailing
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<literal>=</literal>. After this function has been executed successfully the field values may be queried
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using <function>sd_journal_enumerate_unique()</function> and
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<function>sd_journal_enumerate_available_unique()</function>. Invoking one of those calls will change the
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field name being queried and reset the enumeration index to the first field value that matches.</para>
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<para><function>sd_journal_enumerate_unique()</function> may be
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used to iterate through all data fields which match the previously
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selected field name as set with
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<function>sd_journal_query_unique()</function>. On each invocation
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the next field data matching the field name is returned. The order
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of the returned data fields is not defined. It takes three
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arguments: the journal context object, plus a pair of pointers to
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pointer/size variables where the data object and its size shall be
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stored in. The returned data is in a read-only memory map and is
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only valid until the next invocation of
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<function>sd_journal_enumerate_unique()</function>. Note that the
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data returned will be prefixed with the field name and '='. Note
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that this call is subject to the data field size threshold as
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controlled by
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<function>sd_journal_set_data_threshold()</function>.</para>
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<para><function>sd_journal_enumerate_unique()</function> may be used to iterate through all data fields
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which match the previously selected field name as set with
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<function>sd_journal_query_unique()</function>. On each invocation the next field data matching the field
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name is returned. The order of the returned data fields is not defined. It takes three arguments: the
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journal object, plus a pair of pointers to pointer/size variables where the data object and its size
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shall be stored. The returned data is in a read-only memory map and is only valid until the next
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invocation of <function>sd_journal_enumerate_unique()</function>. Note that the data returned will be
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prefixed with the field name and <literal>=</literal>. Note that this call is subject to the data field
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size threshold as controlled by <function>sd_journal_set_data_threshold()</function> and only the initial
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part of the field up to the threshold is returned. An error is returned for fields which cannot be
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retrieved. See the error list below for details.</para>
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<para><function>sd_journal_enumerate_available_unique()</function> is similar to
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<function>sd_journal_enumerate_unique()</function>, but silently skips any fields which may be valid, but
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are too large or not supported by current implementation.</para>
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<para><function>sd_journal_restart_unique()</function> resets the
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data enumeration index to the beginning of the list. The next
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@ -92,11 +98,9 @@
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will return the first field data matching the field name
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again.</para>
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<para>Note that the
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<function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro may be used
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as a handy wrapper around
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<function>sd_journal_restart_unique()</function> and
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<function>sd_journal_enumerate_unique()</function>.</para>
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<para>Note that the <function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro may be used as a handy wrapper
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around <function>sd_journal_restart_unique()</function> and
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<function>sd_journal_enumerate_available_unique()</function>.</para>
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<para>Note that these functions currently are not influenced by
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matches set with <function>sd_journal_add_match()</function> but
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@ -111,13 +115,29 @@
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<refsect1>
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<title>Return Value</title>
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<para><function>sd_journal_query_unique()</function> returns 0 on
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success or a negative errno-style error code.
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<function>sd_journal_enumerate_unique()</function> returns a
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positive integer if the next field data has been read, 0 when no
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more fields are known, or a negative errno-style error code.
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<function>sd_journal_restart_unique()</function> returns
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nothing.</para>
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<para><function>sd_journal_query_unique()</function> returns 0 on success or a negative errno-style error
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code. <function>sd_journal_enumerate_unique()</function> and and
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<function>sd_journal_query_available_unique()</function> return a positive integer if the next field data
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has been read, 0 when no more fields remain, or a negative errno-style error code.
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<function>sd_journal_restart_unique()</function> doesn't return anything.</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<xi:include href="sd_journal_get_data.xml" xpointer="EINVAL"/>
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<xi:include href="sd_journal_get_data.xml" xpointer="ECHILD"/>
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<xi:include href="sd_journal_get_data.xml" xpointer="EADDRNOTAVAIL"/>
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<xi:include href="sd_journal_get_data.xml" xpointer="ENOENT"/>
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<xi:include href="sd_journal_get_data.xml" xpointer="ENOBUFS"/>
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<xi:include href="sd_journal_get_data.xml" xpointer="E2BIG"/>
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<xi:include href="sd_journal_get_data.xml" xpointer="EPROTONOSUPPORT"/>
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<xi:include href="sd_journal_get_data.xml" xpointer="EBADMSG"/>
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<xi:include href="sd_journal_get_data.xml" xpointer="EIO"/>
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</variablelist>
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</refsect2>
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</refsect1>
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<refsect1>
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@ -131,10 +151,9 @@
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<refsect1>
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<title>Examples</title>
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<para>Use the <function>SD_JOURNAL_FOREACH_UNIQUE</function> macro
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to iterate through all values a field of the journal can take. The
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following example lists all unit names referenced in the
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journal:</para>
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<para>Use the <function>SD_JOURNAL_FOREACH_UNIQUE</function> macro to iterate through all values a field
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of the journal can take (and which can be accessed on the given architecture and are not compressed with
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an unsupported mechanism). The following example lists all unit names referenced in the journal:</para>
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<programlisting><xi:include href="journal-iterate-unique.c" parse="text" /></programlisting>
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</refsect1>
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