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| author | Michael Stapelberg <michael@stapelberg.de> | 2014-04-26 10:08:46 +0200 |
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| committer | Michael Stapelberg <michael@stapelberg.de> | 2014-04-26 10:08:46 +0200 |
| commit | 663996b3bb3cdaa81ac830674fdda00e28a2485b (patch) | |
| tree | ec5ccfae391a7cc7970f7618a58970c87dec770b /man/SD_JOURNAL_FOREACH_BACKWARDS.html | |
| download | systemd-663996b3bb3cdaa81ac830674fdda00e28a2485b.tar.gz | |
Imported Upstream version 204
Diffstat (limited to 'man/SD_JOURNAL_FOREACH_BACKWARDS.html')
| -rw-r--r-- | man/SD_JOURNAL_FOREACH_BACKWARDS.html | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/man/SD_JOURNAL_FOREACH_BACKWARDS.html b/man/SD_JOURNAL_FOREACH_BACKWARDS.html new file mode 100644 index 0000000000..7a5cd7c414 --- /dev/null +++ b/man/SD_JOURNAL_FOREACH_BACKWARDS.html @@ -0,0 +1,100 @@ +<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_journal_next</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style> + a.headerlink { + color: #c60f0f; + font-size: 0.8em; + padding: 0 4px 0 4px; + text-decoration: none; + visibility: hidden; + } + + a.headerlink:hover { + background-color: #c60f0f; + color: white; + } + + h1:hover > a.headerlink, h2:hover > a.headerlink, h3:hover > a.headerlink, dt:hover > a.headerlink { + visibility: visible; + } + </style><a href="index.html">Index </a>· + <a href="systemd.directives.html">Directives </a>· + <a href="../python-systemd/index.html">Python </a>· + <a href="../libudev/index.html">libudev </a>· + <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 204</span><hr><div class="refentry"><a name="sd_journal_next"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_journal_next, sd_journal_previous, sd_journal_next_skip, sd_journal_previous_skip, SD_JOURNAL_FOREACH, SD_JOURNAL_FOREACH_BACKWARDS — Advance or set back the read pointer in the journal</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_next</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">int <b class="fsfunc">sd_journal_previous</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">int <b class="fsfunc">sd_journal_next_skip</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>uint64_t <var class="pdparam">skip</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_previous_skip</b>(</code></td><td>sd_journal* <var class="pdparam">j</var>, </td></tr><tr><td> </td><td>uint64_t <var class="pdparam">skip</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</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_BACKWARDS</b>(</code></td><td>sd_journal* <var class="pdparam">j</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm259772947248"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_journal_next()</code> advances + the read pointer into the journal by one entry. The + only argument taken is a journal context object as + allocated via + <a href="sd_journal_open.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_open</span>(3)</span></a>. After + successful invocation the entry may be read with + functions such as + <a href="sd_journal_get_data.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_data</span>(3)</span></a>.</p><p>Similar, <code class="function">sd_journal_previous()</code> sets + the read pointer back one entry.</p><p><code class="function">sd_journal_next_skip()</code> and + <code class="function">sd_journal_previous_skip()</code> + advance/set back the read pointer by multiple entries + at once, as specified in the <code class="varname">skip</code> + parameter.</p><p>The journal is strictly ordered by reception + time, and hence advancing to the next entry guarantees + that the entry then pointing to is later in time than + then previous one, or has the same timestamp.</p><p>Note that + <a href="sd_journal_get_data.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_data</span>(3)</span></a> + and related calls will fail unless + <code class="function">sd_journal_next()</code> has been + invoked at least once in order to position the read + pointer on a journal entry.</p><p>Note that the + <code class="function">SD_JOURNAL_FOREACH()</code> macro may be used + as a wrapper around + <a href="sd_journal_seek_head.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_seek_head</span>(3)</span></a> + and <code class="function">sd_journal_next()</code> in order to + make iterating through the journal easier. See below + for an example. Similar, + <code class="function">SD_JOURNAL_FOREACH_BACKWARDS()</code> + may be used for iterating the journal in reverse + order.</p></div><div class="refsect1"><a name="idm259772933856"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>The four calls return the number of entries + advanced/set back on success or a negative errno-style + error code. When the end or beginning of the journal + is reached, a number smaller than requested is + returned. More specifically, if + <code class="function">sd_journal_next()</code> or + <code class="function">sd_journal_previous()</code> reach the + end/beginning of the journal they will return 0, + instead of 1 when they are successful. This should be + considered an EOF marker.</p></div><div class="refsect1"><a name="idm259772923184"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>The <code class="function">sd_journal_next()</code>, <code class="function">sd_journal_previous()</code>, + <code class="function">sd_journal_next_skip()</code> and + <code class="function">sd_journal_previous_skip()</code> interfaces are + available as shared library, which can be compiled and + linked to with the + <code class="literal">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="idm259772917408"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples">¶</a></h2><p>Iterating through the journal:</p><pre class="programlisting">#include <stdio.h> +#include <string.h> +#include <systemd/sd-journal.h> + +int main(int argc, char *argv[]) { + int r; + sd_journal *j; + r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY); + if (r < 0) { + fprintf(stderr, "Failed to open journal: %s\n", strerror(-r)); + return 1; + } + SD_JOURNAL_FOREACH(j) { + const char *d; + size_t l; + + r = sd_journal_get_data(j, "MESSAGE", &d, &l); + if (r < 0) { + fprintf(stderr, "Failed to read message field: %s\n", strerror(-r)); + continue; + } + + printf("%.*s\n", (int) l, d); + } + sd_journal_close(j); + return 0; +}</pre></div><div class="refsect1"><a name="idm259772914160"></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="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_get_data.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_data</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_get_cursor.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_get_cursor</span>(3)</span></a> + </p></div></div></body></html> |