mirror of
https://github.com/systemd/systemd.git
synced 2024-12-18 14:43:33 +08:00
277 lines
12 KiB
XML
277 lines
12 KiB
XML
<?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>
|