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<refentry id="sd_journal_get_data">
- <refentryinfo>
- <title>sd_journal_get_data</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_get_data</refentrytitle>
- <manvolnum>3</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>sd_journal_get_data</refname>
- <refname>sd_journal_enumerate_data</refname>
- <refname>sd_journal_restart_data</refname>
- <refname>SD_JOURNAL_FOREACH_DATA</refname>
- <refname>sd_journal_set_data_threshold</refname>
- <refname>sd_journal_get_data_threshold</refname>
- <refpurpose>Read data fields from the current journal entry</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_get_data</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>const char *<parameter>field</parameter></paramdef>
- <paramdef>const void **<parameter>data</parameter></paramdef>
- <paramdef>size_t *<parameter>length</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_enumerate_data</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>const void **<parameter>data</parameter></paramdef>
- <paramdef>size_t *<parameter>length</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>void <function>sd_journal_restart_data</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef><function>SD_JOURNAL_FOREACH_DATA</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>const void *<parameter>data</parameter></paramdef>
- <paramdef>size_t <parameter>length</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_set_data_threshold</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>size_t <parameter>sz</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_get_data_threshold</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>size_t *<parameter>sz</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para><function>sd_journal_get_data()</function> gets
- the data object associated with a specific field from
- the current journal entry. It takes four arguments:
- the journal context object, a string with the field
- name to request, plus a pair of pointers to
- pointer/size variables where the data object and its
- size shall be stored in. The field name should be an
- entry field name. Well-known field names are listed in
- <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
- returned data is in a read-only memory map and is only
- valid until the next invocation of
- <function>sd_journal_get_data()</function> or
- <function>sd_journal_enumerate_data()</function>, or
- the read pointer is altered. Note that the data
- returned will be prefixed with the field name and
- '='. Also note that by default data fields larger than
- 64K might get truncated to 64K. This threshold may be
- changed and turned off with
- <function>sd_journal_set_data_threshold()</function> (see
- below).</para>
-
- <para><function>sd_journal_enumerate_data()</function>
- may be used to iterate through all fields of the
- current entry. On each invocation the data for the
- next field is returned. The order of these fields is
- not defined. The data returned is in the same format
- as with <function>sd_journal_get_data()</function> and
- also follows the same life-time semantics.</para>
-
- <para><function>sd_journal_restart_data()</function>
- resets the data enumeration index to the beginning of
- the entry. The next invocation of
- <function>sd_journal_enumerate_data()</function> will return the first
- field of the entry again.</para>
-
- <para>Note that the
- <function>SD_JOURNAL_FOREACH_DATA()</function> macro
- may be used as a handy wrapper around
- <function>sd_journal_restart_data()</function> and
- <function>sd_journal_enumerate_data()</function>.</para>
-
- <para>Note that these functions will not work before
- <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- (or related call) has been called at least
- once, in order to position the read pointer at a valid entry.</para>
-
- <para><function>sd_journal_set_data_threshold()</function>
- may be used to change the data field size threshold
- for data returned by
- <function>sd_journal_get_data()</function>,
- <function>sd_journal_enumerate_data()</function> and
- <function>sd_journal_enumerate_unique()</function>. This
- threshold is a hint only: it indicates that the client
- program is interested only in the initial parts of the
- data fields, up to the threshold in size -- but the
- library might still return larger data objects. That
- means applications should not rely exclusively on this
- setting to limit the size of the data fields returned,
- but need to apply a explicit size limit on the
- returned data as well. This threshold defaults to 64K
- by default. To retrieve the complete data fields this
- threshold should be turned off by setting it to 0, so
- that the library always returns the complete data
- objects. It is recommended to set this threshold as
- low as possible since this relieves the library from
- having to decompress large compressed data objects in
- full.</para>
-
- <para><function>sd_journal_get_data_threshold()</function>
- returns the currently configured data field size
- threshold.</para>
- </refsect1>
-
- <refsect1>
- <title>Return Value</title>
-
- <para><function>sd_journal_get_data()</function>
- returns 0 on success or a negative errno-style error
- code. If the current entry does not include the
- specified field, -ENOENT is returned. If
- <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- has not been called at least once, -EADDRNOTAVAIL is
- returned. <function>sd_journal_enumerate_data()</function>
- returns a positive integer if the next field has been
- read, 0 when no more fields are known, or a negative
- errno-style error
- code. <function>sd_journal_restart_data()</function>
- returns
- nothing. <function>sd_journal_set_data_threshold()</function>
- and <function>sd_journal_get_threshold()</function>
- return 0 on success or a negative errno-style error
- code.</para>
- </refsect1>
-
- <refsect1>
- <title>Notes</title>
-
- <para>The <function>sd_journal_get_data()</function>,
- <function>sd_journal_enumerate_data()</function>,
- <function>sd_journal_restart_data()</function>,
- <function>sd_journal_set_data_threshold()</function>
- and
- <function>sd_journal_get_data_threshold()</function>
- interfaces are available as a shared library, which can
- be compiled and linked to with the
- <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- file.</para>
- </refsect1>
-
- <refsect1>
- <title>Examples</title>
-
- <para>See
- <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- for a complete example how to use
- <function>sd_journal_get_data()</function>.</para>
-
- <para>Use the
- <function>SD_JOURNAL_FOREACH_DATA</function> macro to
- iterate through all fields of the current journal
- entry:</para>
-
- <programlisting>...
+ <refentryinfo>
+ <title>sd_journal_get_data</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_get_data</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_journal_get_data</refname>
+ <refname>sd_journal_enumerate_data</refname>
+ <refname>sd_journal_restart_data</refname>
+ <refname>SD_JOURNAL_FOREACH_DATA</refname>
+ <refname>sd_journal_set_data_threshold</refname>
+ <refname>sd_journal_get_data_threshold</refname>
+ <refpurpose>Read data fields from the current journal entry</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_get_data</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>const char *<parameter>field</parameter></paramdef>
+ <paramdef>const void **<parameter>data</parameter></paramdef>
+ <paramdef>size_t *<parameter>length</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_enumerate_data</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>const void **<parameter>data</parameter></paramdef>
+ <paramdef>size_t *<parameter>length</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>void <function>sd_journal_restart_data</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef><function>SD_JOURNAL_FOREACH_DATA</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>const void *<parameter>data</parameter></paramdef>
+ <paramdef>size_t <parameter>length</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_set_data_threshold</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>size_t <parameter>sz</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_get_data_threshold</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>size_t *<parameter>sz</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_journal_get_data()</function> gets the data
+ object associated with a specific field from the current journal
+ entry. It takes four arguments: the journal context object, a
+ string with the field name to request, plus a pair of pointers to
+ pointer/size variables where the data object and its size shall be
+ stored in. The field name should be an entry field name.
+ Well-known field names are listed in
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ The returned data is in a read-only memory map and is only valid
+ until the next invocation of
+ <function>sd_journal_get_data()</function> or
+ <function>sd_journal_enumerate_data()</function>, or the read
+ pointer is altered. Note that the data returned will be prefixed
+ with the field name and '='. Also note that by default data fields
+ larger than 64K might get truncated to 64K. This threshold may be
+ changed and turned off with
+ <function>sd_journal_set_data_threshold()</function> (see
+ below).</para>
+
+ <para><function>sd_journal_enumerate_data()</function> may be used
+ to iterate through all fields of the current entry. On each
+ invocation the data for the next field is returned. The order of
+ these fields is not defined. The data returned is in the same
+ format as with <function>sd_journal_get_data()</function> and also
+ follows the same life-time semantics.</para>
+
+ <para><function>sd_journal_restart_data()</function> resets the
+ data enumeration index to the beginning of the entry. The next
+ invocation of <function>sd_journal_enumerate_data()</function>
+ will return the first field of the entry again.</para>
+
+ <para>Note that the <function>SD_JOURNAL_FOREACH_DATA()</function>
+ macro may be used as a handy wrapper around
+ <function>sd_journal_restart_data()</function> and
+ <function>sd_journal_enumerate_data()</function>.</para>
+
+ <para>Note that these functions will not work before
+ <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ (or related call) has been called at least once, in order to
+ position the read pointer at a valid entry.</para>
+
+ <para><function>sd_journal_set_data_threshold()</function> may be
+ used to change the data field size threshold for data returned by
+ <function>sd_journal_get_data()</function>,
+ <function>sd_journal_enumerate_data()</function> and
+ <function>sd_journal_enumerate_unique()</function>. This threshold
+ is a hint only: it indicates that the client program is interested
+ only in the initial parts of the data fields, up to the threshold
+ in size -- but the library might still return larger data objects.
+ That means applications should not rely exclusively on this
+ setting to limit the size of the data fields returned, but need to
+ apply a explicit size limit on the returned data as well. This
+ threshold defaults to 64K by default. To retrieve the complete
+ data fields this threshold should be turned off by setting it to
+ 0, so that the library always returns the complete data objects.
+ It is recommended to set this threshold as low as possible since
+ this relieves the library from having to decompress large
+ compressed data objects in full.</para>
+
+ <para><function>sd_journal_get_data_threshold()</function> returns
+ the currently configured data field size threshold.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para><function>sd_journal_get_data()</function> returns 0 on
+ success or a negative errno-style error code. If the current entry
+ does not include the specified field, -ENOENT is returned. If
+ <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ has not been called at least once, -EADDRNOTAVAIL is returned.
+ <function>sd_journal_enumerate_data()</function> returns a
+ positive integer if the next field has been read, 0 when no more
+ fields are known, or a negative errno-style error code.
+ <function>sd_journal_restart_data()</function> returns nothing.
+ <function>sd_journal_set_data_threshold()</function> and
+ <function>sd_journal_get_threshold()</function> return 0 on
+ success or a negative errno-style error code.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>The <function>sd_journal_get_data()</function>,
+ <function>sd_journal_enumerate_data()</function>,
+ <function>sd_journal_restart_data()</function>,
+ <function>sd_journal_set_data_threshold()</function> and
+ <function>sd_journal_get_data_threshold()</function> interfaces
+ are available as a shared library, which can be compiled and
+ linked to with the
+ <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ file.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <para>See
+ <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for a complete example how to use
+ <function>sd_journal_get_data()</function>.</para>
+
+ <para>Use the
+ <function>SD_JOURNAL_FOREACH_DATA</function> macro to
+ iterate through all fields of the current journal
+ entry:</para>
+
+ <programlisting>...
int print_fields(sd_journal *j) {
- const void *data;
- size_t length;
- SD_JOURNAL_FOREACH_DATA(j, data, length)
- printf("%.*s\n", (int) length, data);
+ const void *data;
+ size_t length;
+ SD_JOURNAL_FOREACH_DATA(j, data, length)
+ printf("%.*s\n", (int) length, data);
}
...</programlisting>
- </refsect1>
-
- <refsect1>
- <title>See Also</title>
-
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</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_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_query_unique</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- </para>
- </refsect1>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</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_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_query_unique</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
</refentry>
~ianmdlvl / elogind.git / blobdiff