5784N/A<?
xml version='1.0'?>
<!--*-nxml-*--> 5784N/A<!
DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" 5784N/A This file is part of systemd. 5784N/A Copyright 2012 Lennart Poettering 5784N/A systemd is free software; you can redistribute it and/or modify it 5784N/A under the terms of the GNU Lesser General Public License as published by 5784N/A the Free Software Foundation; either version 2.1 of the License, or 5784N/A (at your option) any later version. 5784N/A systemd is distributed in the hope that it will be useful, but 5784N/A WITHOUT ANY WARRANTY; without even the implied warranty of 5784N/A MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 5784N/A Lesser General Public License for more details. 5784N/A You should have received a copy of the GNU Lesser General Public License 5784N/A<
refentry id="sd_journal_get_data">
5784N/A <
title>sd_journal_get_data</
title>
5784N/A <
productname>systemd</
productname>
5784N/A <
contrib>Developer</
contrib>
5784N/A <
firstname>Lennart</
firstname>
5784N/A <
surname>Poettering</
surname>
5784N/A <
email>lennart@poettering.net</
email>
5784N/A <
refentrytitle>sd_journal_get_data</
refentrytitle>
5784N/A <
refname>sd_journal_get_data</
refname>
5784N/A <
refname>sd_journal_enumerate_data</
refname>
5784N/A <
refname>sd_journal_restart_data</
refname>
5784N/A <
refname>SD_JOURNAL_FOREACH_DATA</
refname>
5784N/A <
refname>sd_journal_set_data_threshold</
refname>
5784N/A <
refname>sd_journal_get_data_threshold</
refname>
5784N/A <
refpurpose>Read data fields from the current journal entry</
refpurpose>
5784N/A <
funcdef>int <
function>sd_journal_get_data</
function></
funcdef>
5784N/A <
paramdef>sd_journal *<
parameter>j</
parameter></
paramdef>
5784N/A <
paramdef>const char *<
parameter>field</
parameter></
paramdef>
5784N/A <
paramdef>const void **<
parameter>data</
parameter></
paramdef>
5784N/A <
paramdef>size_t *<
parameter>length</
parameter></
paramdef>
5784N/A <
funcdef>int <
function>sd_journal_enumerate_data</
function></
funcdef>
5784N/A <
paramdef>sd_journal *<
parameter>j</
parameter></
paramdef>
5784N/A <
paramdef>const void **<
parameter>data</
parameter></
paramdef>
5784N/A <
paramdef>size_t *<
parameter>length</
parameter></
paramdef>
5784N/A <
funcdef>void <
function>sd_journal_restart_data</
function></
funcdef>
5784N/A <
paramdef>sd_journal *<
parameter>j</
parameter></
paramdef>
5784N/A <
funcdef><
function>SD_JOURNAL_FOREACH_DATA</
function></
funcdef>
5784N/A <
paramdef>sd_journal *<
parameter>j</
parameter></
paramdef>
5784N/A <
paramdef>const void *<
parameter>data</
parameter></
paramdef>
5784N/A <
paramdef>size_t <
parameter>length</
parameter></
paramdef>
5784N/A <
funcdef>int <
function>sd_journal_set_data_threshold</
function></
funcdef>
5784N/A <
paramdef>sd_journal *<
parameter>j</
parameter></
paramdef>
5784N/A <
paramdef>size_t <
parameter>sz</
parameter></
paramdef>
5784N/A <
funcdef>int <
function>sd_journal_get_data_threshold</
function></
funcdef>
5784N/A <
paramdef>sd_journal *<
parameter>j</
parameter></
paramdef>
5784N/A <
paramdef>size_t *<
parameter>sz</
parameter></
paramdef>
5784N/A <
para><
function>sd_journal_get_data()</
function> gets
5784N/A the data object associated with a specific field from
5784N/A the current journal entry. It takes four arguments:
5784N/A the journal context object, a string with the field
name to request, plus a pair of pointers to
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
<
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>
<
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
<
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
<
para><
function>sd_journal_get_data_threshold()</
function>
returns the currently configured data field size
<
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
code. <
function>sd_journal_restart_data()</
function>
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
<
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>
<
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>
<
citerefentry><
refentrytitle>sd_journal_next</
refentrytitle><
manvolnum>3</
manvolnum></
citerefentry>
for a complete example how to use
<
function>sd_journal_get_data()</
function>.</
para>
<
function>SD_JOURNAL_FOREACH_DATA</
function> macro to
iterate through all fields of the current journal
int print_fields(sd_journal *j) {
SD_JOURNAL_FOREACH_DATA(j, data, length)
printf("%.*s\n", (int) length, data);
<
citerefentry><
refentrytitle>systemd</
refentrytitle><
manvolnum>1</
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>