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| e3bff60a | 22 | <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 220</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="idm140169296629136"></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 |
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23 | object associated with a specific field from the current journal |
| 24 | entry. It takes four arguments: the journal context object, a | |
| 25 | string with the field name to request, plus a pair of pointers to | |
| 26 | pointer/size variables where the data object and its size shall be | |
| 27 | stored in. The field name should be an entry field name. | |
| 28 | Well-known field names are listed in | |
| 29 | <a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>. | |
| 30 | The returned data is in a read-only memory map and is only valid | |
| 31 | until the next invocation of | |
| 32 | <code class="function">sd_journal_get_data()</code> or | |
| 33 | <code class="function">sd_journal_enumerate_data()</code>, or the read | |
| 34 | pointer is altered. Note that the data returned will be prefixed | |
| 35 | with the field name and '='. Also note that by default data fields | |
| 36 | larger than 64K might get truncated to 64K. This threshold may be | |
| 37 | changed and turned off with | |
| 38 | <code class="function">sd_journal_set_data_threshold()</code> (see | |
| 39 | below).</p><p><code class="function">sd_journal_enumerate_data()</code> may be used | |
| 40 | to iterate through all fields of the current entry. On each | |
| 41 | invocation the data for the next field is returned. The order of | |
| 42 | these fields is not defined. The data returned is in the same | |
| 43 | format as with <code class="function">sd_journal_get_data()</code> and also | |
| 44 | follows the same life-time semantics.</p><p><code class="function">sd_journal_restart_data()</code> resets the | |
| 45 | data enumeration index to the beginning of the entry. The next | |
| 46 | invocation of <code class="function">sd_journal_enumerate_data()</code> | |
| 47 | will return the first field of the entry again.</p><p>Note that the <code class="function">SD_JOURNAL_FOREACH_DATA()</code> | |
| 48 | macro may be used as a handy wrapper around | |
| 49 | <code class="function">sd_journal_restart_data()</code> and | |
| 50 | <code class="function">sd_journal_enumerate_data()</code>.</p><p>Note that these functions will not work before | |
| 51 | <a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a> | |
| 52 | (or related call) has been called at least once, in order to | |
| 53 | position the read pointer at a valid entry.</p><p><code class="function">sd_journal_set_data_threshold()</code> may be | |
| 54 | used to change the data field size threshold for data returned by | |
| 55 | <code class="function">sd_journal_get_data()</code>, | |
| 56 | <code class="function">sd_journal_enumerate_data()</code> and | |
| 57 | <code class="function">sd_journal_enumerate_unique()</code>. This threshold | |
| 58 | is a hint only: it indicates that the client program is interested | |
| 59 | only in the initial parts of the data fields, up to the threshold | |
| 60 | in size -- but the library might still return larger data objects. | |
| 61 | That means applications should not rely exclusively on this | |
| 62 | setting to limit the size of the data fields returned, but need to | |
| 63 | apply a explicit size limit on the returned data as well. This | |
| 64 | threshold defaults to 64K by default. To retrieve the complete | |
| 65 | data fields this threshold should be turned off by setting it to | |
| 66 | 0, so that the library always returns the complete data objects. | |
| 67 | It is recommended to set this threshold as low as possible since | |
| 68 | this relieves the library from having to decompress large | |
| 69 | compressed data objects in full.</p><p><code class="function">sd_journal_get_data_threshold()</code> returns | |
| e3bff60a | 70 | the currently configured data field size threshold.</p></div><div class="refsect1"><a name="idm140169296612688"></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 |
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71 | success or a negative errno-style error code. If the current entry |
| 72 | does not include the specified field, -ENOENT is returned. If | |
| 73 | <a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a> | |
| 74 | has not been called at least once, -EADDRNOTAVAIL is returned. | |
| 75 | <code class="function">sd_journal_enumerate_data()</code> returns a | |
| 76 | positive integer if the next field has been read, 0 when no more | |
| 77 | fields are known, or a negative errno-style error code. | |
| 78 | <code class="function">sd_journal_restart_data()</code> returns nothing. | |
| 79 | <code class="function">sd_journal_set_data_threshold()</code> and | |
| 80 | <code class="function">sd_journal_get_threshold()</code> return 0 on | |
| e3bff60a | 81 | success or a negative errno-style error code.</p></div><div class="refsect1"><a name="idm140169296607344"></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>, |
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82 | <code class="function">sd_journal_enumerate_data()</code>, |
| 83 | <code class="function">sd_journal_restart_data()</code>, | |
| 84 | <code class="function">sd_journal_set_data_threshold()</code> and | |
| 85 | <code class="function">sd_journal_get_data_threshold()</code> interfaces | |
| 86 | are available as a shared library, which can be compiled and | |
| 87 | linked to with the | |
| 88 | <code class="constant">libsystemd</code> <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a> | |
| e3bff60a | 89 | file.</p></div><div class="refsect1"><a name="idm140169296601552"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples">¶</a></h2><p>See |
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90 | <a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a> |
| 91 | for a complete example how to use | |
| 92 | <code class="function">sd_journal_get_data()</code>.</p><p>Use the | |
| 93 | <code class="function">SD_JOURNAL_FOREACH_DATA</code> macro to | |
| 94 | iterate through all fields of the current journal | |
| 95 | entry:</p><pre class="programlisting">... | |
| 663996b3 | 96 | int print_fields(sd_journal *j) { |
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97 | const void *data; |
| 98 | size_t length; | |
| 99 | SD_JOURNAL_FOREACH_DATA(j, data, length) | |
| 100 | printf("%.*s\n", (int) length, data); | |
| 663996b3 | 101 | } |
| e3bff60a | 102 | ...</pre></div><div class="refsect1"><a name="idm140169296597104"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p> |
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103 | <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>, |
| 104 | <a href="systemd.journal-fields.html"><span class="citerefentry"><span class="refentrytitle">systemd.journal-fields</span>(7)</span></a>, | |
| 105 | <a href="sd-journal.html"><span class="citerefentry"><span class="refentrytitle">sd-journal</span>(3)</span></a>, | |
| 106 | <a href="sd_journal_open.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_open</span>(3)</span></a>, | |
| 107 | <a href="sd_journal_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>, | |
| 108 | <a href="sd_journal_get_realtime_usec.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_realtime_usec</span>(3)</span></a>, | |
| 109 | <a href="sd_journal_query_unique.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_query_unique</span>(3)</span></a> | |
| 110 | </p></div></div></body></html> |