man/sd_journal_get_data.xml - systemd - Git at Google

 <?xml version='1.0'?> <!--*-nxml-*-->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

 <refentry id="sd_journal_get_data" xmlns:xi="http://www.w3.org/2001/XInclude">

   <refentryinfo>
     <title>sd_journal_get_data</title>
     <productname>systemd</productname>
   </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_enumerate_available_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 &lt;systemd/sd-journal.h&gt;</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>int <function>sd_journal_enumerate_available_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>,
     but any field can be specified. 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>,
     <function>sd_journal_enumerate_data()</function>,
     <function>sd_journal_enumerate_available_data()</function>, or when the read pointer is altered. Note
     that the data returned will be prefixed with the field name and <literal>=</literal>. 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_enumerate_available_data()</function> is similar to
     <function>sd_journal_enumerate_data()</function>, but silently skips any fields which may be valid, but
     are too large or not supported by current implementation.</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_available_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 an 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. <function>sd_journal_enumerate_data()</function> and
     <function>sd_journal_enumerate_available_data()</function> return a positive integer if the next field
     has been read, 0 when no more fields remain, or a negative errno-style error code.
     <function>sd_journal_restart_data()</function> doesn't return anything.
     <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>

     <refsect2>
       <title>Errors</title>

       <para>Returned errors may indicate the following problems:</para>

       <variablelist>
         <varlistentry id='EINVAL'>
           <term><constant>-EINVAL</constant></term>

           <listitem><para>One of the required parameters is <constant>NULL</constant> or invalid.
           </para></listitem>
         </varlistentry>

         <varlistentry id='ECHILD'>
           <term><constant>-ECHILD</constant></term>

           <listitem><para>The journal object was created in a different process.</para></listitem>
         </varlistentry>

         <varlistentry id='EADDRNOTAVAIL'>
           <term><constant>-EADDRNOTAVAIL</constant></term>

           <listitem><para>The read pointer is not positioned at a valid entry;
           <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
           or a related call has not been called at least once.</para></listitem>
         </varlistentry>

         <varlistentry id='ENOENT'>
           <term><constant>-ENOENT</constant></term>

           <listitem><para>The current entry does not include the specified field.</para>
           </listitem>
         </varlistentry>

         <varlistentry id='ENOMEM'>
           <term><constant>-ENOMEM</constant></term>

           <listitem><para>Memory allocation failed.</para></listitem>
         </varlistentry>

         <varlistentry id='ENOBUFS'>
           <term><constant>-ENOBUFS</constant></term>

           <listitem><para>A compressed entry is too large.</para></listitem>
         </varlistentry>

         <varlistentry id='E2BIG'>
           <term><constant>-E2BIG</constant></term>

           <listitem><para>The data field is too large for this computer architecture (e.g. above 4 GB on a
           32-bit architecture).</para></listitem>
         </varlistentry>

         <varlistentry id='EPROTONOSUPPORT'>
           <term><constant>-EPROTONOSUPPORT</constant></term>

           <listitem><para>The journal is compressed with an unsupported method or the journal uses an
           unsupported feature.</para></listitem>
         </varlistentry>

         <varlistentry id='EBADMSG'>
           <term><constant>-EBADMSG</constant></term>

           <listitem><para>The journal is corrupted (possibly just the entry being iterated over).
           </para></listitem>
         </varlistentry>

         <varlistentry id='EIO'>
           <term><constant>-EIO</constant></term>

           <listitem><para>An I/O error was reported by the kernel.</para></listitem>
         </varlistentry>
       </variablelist>
     </refsect2>
   </refsect1>

   <refsect1>
     <title>Notes</title>

     <xi:include href="threads-aware.xml" xpointer="strict"/>

     <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
   </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);
 }
 …</programlisting>
   </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>
	<?xml version='1.0'?> <!---nxml--->
	<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
	"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
	<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

	<refentry id="sd_journal_get_data" xmlns:xi="http://www.w3.org/2001/XInclude">

	<refentryinfo>
	<title>sd_journal_get_data</title>
	<productname>systemd</productname>
	</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_enumerate_available_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>int <function>sd_journal_enumerate_available_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>,
	but any field can be specified. 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>,
	<function>sd_journal_enumerate_data()</function>,
	<function>sd_journal_enumerate_available_data()</function>, or when the read pointer is altered. Note
	that the data returned will be prefixed with the field name and <literal>=</literal>. 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_enumerate_available_data()</function> is similar to
	<function>sd_journal_enumerate_data()</function>, but silently skips any fields which may be valid, but
	are too large or not supported by current implementation.</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_available_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 an 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. <function>sd_journal_enumerate_data()</function> and
	<function>sd_journal_enumerate_available_data()</function> return a positive integer if the next field
	has been read, 0 when no more fields remain, or a negative errno-style error code.
	<function>sd_journal_restart_data()</function> doesn't return anything.
	<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>

	<refsect2>
	<title>Errors</title>

	<para>Returned errors may indicate the following problems:</para>

	<variablelist>
	<varlistentry id='EINVAL'>
	<term><constant>-EINVAL</constant></term>

	<listitem><para>One of the required parameters is <constant>NULL</constant> or invalid.
	</para></listitem>
	</varlistentry>

	<varlistentry id='ECHILD'>
	<term><constant>-ECHILD</constant></term>

	<listitem><para>The journal object was created in a different process.</para></listitem>
	</varlistentry>

	<varlistentry id='EADDRNOTAVAIL'>
	<term><constant>-EADDRNOTAVAIL</constant></term>

	<listitem><para>The read pointer is not positioned at a valid entry;
	<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	or a related call has not been called at least once.</para></listitem>
	</varlistentry>

	<varlistentry id='ENOENT'>
	<term><constant>-ENOENT</constant></term>

	<listitem><para>The current entry does not include the specified field.</para>
	</listitem>
	</varlistentry>

	<varlistentry id='ENOMEM'>
	<term><constant>-ENOMEM</constant></term>

	<listitem><para>Memory allocation failed.</para></listitem>
	</varlistentry>

	<varlistentry id='ENOBUFS'>
	<term><constant>-ENOBUFS</constant></term>

	<listitem><para>A compressed entry is too large.</para></listitem>
	</varlistentry>

	<varlistentry id='E2BIG'>
	<term><constant>-E2BIG</constant></term>

	<listitem><para>The data field is too large for this computer architecture (e.g. above 4 GB on a
	32-bit architecture).</para></listitem>
	</varlistentry>

	<varlistentry id='EPROTONOSUPPORT'>
	<term><constant>-EPROTONOSUPPORT</constant></term>

	<listitem><para>The journal is compressed with an unsupported method or the journal uses an
	unsupported feature.</para></listitem>
	</varlistentry>

	<varlistentry id='EBADMSG'>
	<term><constant>-EBADMSG</constant></term>

	<listitem><para>The journal is corrupted (possibly just the entry being iterated over).
	</para></listitem>
	</varlistentry>

	<varlistentry id='EIO'>
	<term><constant>-EIO</constant></term>

	<listitem><para>An I/O error was reported by the kernel.</para></listitem>
	</varlistentry>
	</variablelist>
	</refsect2>
	</refsect1>

	<refsect1>
	<title>Notes</title>

	<xi:include href="threads-aware.xml" xpointer="strict"/>

	<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
	</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);
	}
	…</programlisting>
	</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>