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  <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 208</span><hr><div class="refentry"><a name="sd_journal_get_data"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_journal_get_data, sd_journal_enumerate_data, sd_journal_restart_data, SD_JOURNAL_FOREACH_DATA, sd_journal_set_data_threshold, sd_journal_get_data_threshold — Read data fields from the current journal entry</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include &lt;systemd/sd-journal.h&gt;</pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_get_data</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>const char* <var class="pdparam">field</var>, </td></tr><tr><td> </td><td>const void** <var class="pdparam">data</var>, </td></tr><tr><td> </td><td>size_t* <var class="pdparam">length</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_enumerate_data</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>const void** <var class="pdparam">data</var>, </td></tr><tr><td> </td><td>size_t* <var class="pdparam">length</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">sd_journal_restart_data</b>(</code></td><td>sd_journal* <var class="pdparam">j</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef"><b class="fsfunc">SD_JOURNAL_FOREACH_DATA</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>const void* <var class="pdparam">data</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_set_data_threshold</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">sz</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_get_data_threshold</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>size_t* <var class="pdparam">sz</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm274684373776"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_journal_get_data()</code> 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
                <a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>. The
                returned data is in a read-only memory map and is only
                valid until the next invocation of
                <code class="function">sd_journal_get_data()</code> or
                <code class="function">sd_journal_enumerate_data()</code>, 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
                <code class="function">sd_journal_set_data_threshold()</code> (see
                below).</p><p><code class="function">sd_journal_enumerate_data()</code>
                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 <code class="function">sd_journal_get_data()</code> and
                also follows the same life-time semantics.</p><p><code class="function">sd_journal_restart_data()</code>
                resets the data enumeration index to the beginning of
                the entry. The next invocation of
                <code class="function">sd_journal_enumerate_data()</code> will return the first
                field of the entry again.</p><p>Note that the
                <code class="function">SD_JOURNAL_FOREACH_DATA()</code> macro
                may be used as a handy wrapper around
                <code class="function">sd_journal_restart_data()</code> and
                <code class="function">sd_journal_enumerate_data()</code>.</p><p>Note that these functions will not work before
                <a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
                (or related call) has been called at least
                once, in order to position the read pointer at a valid entry.</p><p><code class="function">sd_journal_set_data_threshold()</code>
                may be used to change the data field size threshold
                for data returned by
                <code class="function">sd_journal_get_data()</code>,
                <code class="function">sd_journal_enumerate_data()</code> and
                <code class="function">sd_journal_enumerate_unique()</code>. 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.</p><p><code class="function">sd_journal_get_data_threshold()</code>
                returns the currently configured data field size
                threshold.</p></div><div class="refsect1"><a name="idm274684347840"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p><code class="function">sd_journal_get_data()</code>
                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
                <a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
                has not been called at least once, -EADDRNOTAVAIL is
                returned. <code class="function">sd_journal_enumerate_data()</code>
                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. <code class="function">sd_journal_restart_data()</code>
                returns
                nothing. <code class="function">sd_journal_set_data_threshold()</code>
                and <code class="function">sd_journal_get_threshold()</code>
                return 0 on success or a negative errno-style error
                code.</p></div><div class="refsect1"><a name="idm274684341792"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The <code class="function">sd_journal_get_data()</code>,
                <code class="function">sd_journal_enumerate_data()</code>,
                <code class="function">sd_journal_restart_data()</code>,
                <code class="function">sd_journal_set_data_threshold()</code>
                and
                <code class="function">sd_journal_get_data_threshold()</code>
                interfaces are available as shared library, which can
                be compiled and linked to with the
                <code class="constant">libsystemd-journal</code> <a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
                file.</p></div><div class="refsect1"><a name="idm274679375856"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples">¶</a></h2><p>See
                <a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
                for a complete example how to use
                <code class="function">sd_journal_get_data()</code>.</p><p>Use the
                <code class="function">SD_JOURNAL_FOREACH_DATA</code> macro to
                iterate through all fields of the current journal
                entry:</p><pre class="programlisting">...
int print_fields(sd_journal *j) {
        const void *data;
        size_t l;
        SD_JOURNAL_FOREACH_DATA(j, data, length)
                printf("%.*s\n", (int) length, data);
}
...</pre></div><div class="refsect1"><a name="idm274679371360"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
                        <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
                        <a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>,
                        <a href="sd-journal.html"><span class="citerefentry"><span class="refentrytitle">sd-journal</span>(3)</span></a>,
                        <a href="sd_journal_open.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_open</span>(3)</span></a>,
                        <a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>,
                        <a href="sd_journal_get_realtime_usec.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_realtime_usec</span>(3)</span></a>,
                        <a href="sd_journal_query_unique.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_query_unique</span>(3)</span></a>
                </p></div></div></body></html>
Commit	Line	Data
663996b3 MS	1	<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_journal_get_data</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
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	18	</style><a href="index.html">Index </a>·
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14228c0d	22	<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 208</span><hr><div class="refentry"><a name="sd_journal_get_data"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_journal_get_data, sd_journal_enumerate_data, sd_journal_restart_data, SD_JOURNAL_FOREACH_DATA, sd_journal_set_data_threshold, sd_journal_get_data_threshold — Read data fields from the current journal entry</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-journal.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_get_data</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>const char* <var class="pdparam">field</var>, </td></tr><tr><td> </td><td>const void** <var class="pdparam">data</var>, </td></tr><tr><td> </td><td>size_t* <var class="pdparam">length</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_enumerate_data</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>const void** <var class="pdparam">data</var>, </td></tr><tr><td> </td><td>size_t* <var class="pdparam">length</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">sd_journal_restart_data</b>(</code></td><td>sd_journal* <var class="pdparam">j</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef"><b class="fsfunc">SD_JOURNAL_FOREACH_DATA</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>const void* <var class="pdparam">data</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_set_data_threshold</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">sz</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_journal_get_data_threshold</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>size_t* <var class="pdparam">sz</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm274684373776"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_journal_get_data()</code> gets
663996b3 MS	23	the data object associated with a specific field from
	24	the current journal entry. It takes four arguments:
	25	the journal context object, a string with the field
	26	name to request, plus a pair of pointers to
	27	pointer/size variables where the data object and its
	28	size shall be stored in. The field name should be an
	29	entry field name. Well-known field names are listed in
	30	<a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>. The
	31	returned data is in a read-only memory map and is only
	32	valid until the next invocation of
	33	<code class="function">sd_journal_get_data()</code> or
	34	<code class="function">sd_journal_enumerate_data()</code>, or
	35	the read pointer is altered. Note that the data
	36	returned will be prefixed with the field name and
	37	'='. Also note that by default data fields larger than
	38	64K might get truncated to 64K. This threshold may be
	39	changed and turned off with
	40	<code class="function">sd_journal_set_data_threshold()</code> (see
	41	below).</p><p><code class="function">sd_journal_enumerate_data()</code>
	42	may be used to iterate through all fields of the
	43	current entry. On each invocation the data for the
	44	next field is returned. The order of these fields is
	45	not defined. The data returned is in the same format
	46	as with <code class="function">sd_journal_get_data()</code> and
	47	also follows the same life-time semantics.</p><p><code class="function">sd_journal_restart_data()</code>
	48	resets the data enumeration index to the beginning of
	49	the entry. The next invocation of
	50	<code class="function">sd_journal_enumerate_data()</code> will return the first
	51	field of the entry again.</p><p>Note that the
	52	<code class="function">SD_JOURNAL_FOREACH_DATA()</code> macro
	53	may be used as a handy wrapper around
	54	<code class="function">sd_journal_restart_data()</code> and
	55	<code class="function">sd_journal_enumerate_data()</code>.</p><p>Note that these functions will not work before
	56	<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
	57	(or related call) has been called at least
	58	once, in order to position the read pointer at a valid entry.</p><p><code class="function">sd_journal_set_data_threshold()</code>
	59	may be used to change the data field size threshold
	60	for data returned by
	61	<code class="function">sd_journal_get_data()</code>,
	62	<code class="function">sd_journal_enumerate_data()</code> and
	63	<code class="function">sd_journal_enumerate_unique()</code>. This
	64	threshold is a hint only: it indicates that the client
	65	program is interested only in the initial parts of the
	66	data fields, up to the threshold in size -- but the
	67	library might still return larger data objects. That
	68	means applications should not rely exclusively on this
	69	setting to limit the size of the data fields returned,
	70	but need to apply a explicit size limit on the
	71	returned data as well. This threshold defaults to 64K
	72	by default. To retrieve the complete data fields this
	73	threshold should be turned off by setting it to 0, so
	74	that the library always returns the complete data
	75	objects. It is recommended to set this threshold as
	76	low as possible since this relieves the library from
	77	having to decompress large compressed data objects in
	78	full.</p><p><code class="function">sd_journal_get_data_threshold()</code>
	79	returns the currently configured data field size
14228c0d	80	threshold.</p></div><div class="refsect1"><a name="idm274684347840"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p><code class="function">sd_journal_get_data()</code>
663996b3 MS	81	returns 0 on success or a negative errno-style error
663996b3 MS	82	code. If the current entry does not include the
14228c0d	83	specified field, -ENOENT is returned. If
663996b3	84	<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
14228c0d	85	has not been called at least once, -EADDRNOTAVAIL is
663996b3 MS	86	returned. <code class="function">sd_journal_enumerate_data()</code>
	87	returns a positive integer if the next field has been
	88	read, 0 when no more fields are known, or a negative
	89	errno-style error
	90	code. <code class="function">sd_journal_restart_data()</code>
	91	returns
	92	nothing. <code class="function">sd_journal_set_data_threshold()</code>
	93	and <code class="function">sd_journal_get_threshold()</code>
	94	return 0 on success or a negative errno-style error
14228c0d	95	code.</p></div><div class="refsect1"><a name="idm274684341792"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The <code class="function">sd_journal_get_data()</code>,
663996b3 MS	96	<code class="function">sd_journal_enumerate_data()</code>,
	97	<code class="function">sd_journal_restart_data()</code>,
	98	<code class="function">sd_journal_set_data_threshold()</code>
	99	and
	100	<code class="function">sd_journal_get_data_threshold()</code>
	101	interfaces are available as shared library, which can
	102	be compiled and linked to with the
14228c0d MB	103	<code class="constant">libsystemd-journal</code> <a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
14228c0d MB	104	file.</p></div><div class="refsect1"><a name="idm274679375856"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples">¶</a></h2><p>See
663996b3 MS	105	<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>
	106	for a complete example how to use
	107	<code class="function">sd_journal_get_data()</code>.</p><p>Use the
	108	<code class="function">SD_JOURNAL_FOREACH_DATA</code> macro to
	109	iterate through all fields of the current journal
	110	entry:</p><pre class="programlisting">...
	111	int print_fields(sd_journal *j) {
	112	const void *data;
	113	size_t l;
	114	SD_JOURNAL_FOREACH_DATA(j, data, length)
	115	printf("%.*s\n", (int) length, data);
	116	}
14228c0d	117	...</pre></div><div class="refsect1"><a name="idm274679371360"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
663996b3 MS	118	<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
	119	<a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>,
	120	<a href="sd-journal.html"><span class="citerefentry"><span class="refentrytitle">sd-journal</span>(3)</span></a>,
	121	<a href="sd_journal_open.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_open</span>(3)</span></a>,
	122	<a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>,
	123	<a href="sd_journal_get_realtime_usec.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_realtime_usec</span>(3)</span></a>,
	124	<a href="sd_journal_query_unique.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_query_unique</span>(3)</span></a>
	125	</p></div></div></body></html>