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diff --git a/man/sd_journal_get_timeout.html b/man/sd_journal_get_timeout.html deleted file mode 100644 index 2da5ccc857..0000000000 --- a/man/sd_journal_get_timeout.html +++ /dev/null @@ -1,201 +0,0 @@ -<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>sd_journal_get_fd</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>· - - <span style="float:right">systemd 221</span><hr><div class="refentry"><a name="sd_journal_get_fd"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_journal_get_fd, sd_journal_get_events, sd_journal_get_timeout, sd_journal_process, sd_journal_wait, sd_journal_reliable_fd, SD_JOURNAL_NOP, SD_JOURNAL_APPEND, SD_JOURNAL_INVALIDATE — Journal change notification - interface</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_fd</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_get_events</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_get_timeout</b>(</code></td><td>sd_journal *<var class="pdparam">j</var>, </td></tr><tr><td> </td><td>uint64_t *<var class="pdparam">timeout_usec</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_process</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_wait</b>(</code></td><td>sd_journal *<var class="pdparam">j</var>, </td></tr><tr><td> </td><td>uint64_t <var class="pdparam">timeout_usec</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_reliable_fd</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="idm47966626767184"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_journal_get_fd()</code> returns a file - descriptor that may be asynchronously polled in an external event - loop and is signaled as soon as the journal changes, because new - entries or files were added, rotation took place, or files have - been deleted, and similar. The file descriptor is suitable for - usage in - <a href="http://man7.org/linux/man-pages/man2/poll.2.html"><span class="citerefentry"><span class="refentrytitle">poll</span>(2)</span></a>. - Use <code class="function">sd_journal_get_events()</code> for an events - mask to watch for. The call takes one argument: the journal - context object. Note that not all file systems are capable of - generating the necessary events for wakeups from this file - descriptor for changes to be noticed immediately. In particular - network files systems do not generate suitable file change events - in all cases. Cases like this can be detected with - <code class="function">sd_journal_reliable_fd()</code>, below. - <code class="function">sd_journal_get_timeout()</code> will ensure in these - cases that wake-ups happen frequently enough for changes to be - noticed, although with a certain latency.</p><p><code class="function">sd_journal_get_events()</code> will return the - <code class="function">poll()</code> mask to wait for. This function will - return a combination of <code class="constant">POLLIN</code> and - <code class="constant">POLLOUT</code> and similar to fill into the - "<code class="literal">.events</code>" field of <code class="varname">struct - pollfd</code>.</p><p><code class="function">sd_journal_get_timeout()</code> will return a - timeout value for usage in <code class="function">poll()</code>. This - returns a value in microseconds since the epoch of - <code class="constant">CLOCK_MONOTONIC</code> for timing out - <code class="function">poll()</code> in <code class="varname">timeout_usec</code>. - See - <a href="http://man7.org/linux/man-pages/man2/clock_gettime.2.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a> - for details about <code class="constant">CLOCK_MONOTONIC</code>. If there - is no timeout to wait for, this will fill in <code class="constant">(uint64_t) - -1</code> instead. Note that <code class="function">poll()</code> takes - a relative timeout in milliseconds rather than an absolute timeout - in microseconds. To convert the absolute 'us' timeout into - relative 'ms', use code like the following:</p><pre class="programlisting">uint64_t t; -int msec; -sd_journal_get_timeout(m, &t); -if (t == (uint64_t) -1) - msec = -1; -else { - struct timespec ts; - uint64_t n; - clock_getttime(CLOCK_MONOTONIC, &ts); - n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000; - msec = t > n ? (int) ((t - n + 999) / 1000) : 0; -}</pre><p>The code above does not do any error checking for brevity's - sake. The calculated <code class="varname">msec</code> integer can be passed - directly as <code class="function">poll()</code>'s timeout - parameter.</p><p>After each <code class="function">poll()</code> wake-up - <code class="function">sd_journal_process()</code> needs to be called to - process events. This call will also indicate what kind of change - has been detected (see below; note that spurious wake-ups are - possible).</p><p>A synchronous alternative for using - <code class="function">sd_journal_get_fd()</code>, - <code class="function">sd_journal_get_events()</code>, - <code class="function">sd_journal_get_timeout()</code> and - <code class="function">sd_journal_process()</code> is - <code class="function">sd_journal_wait()</code>. It will synchronously wait - until the journal gets changed. The maximum time this call sleeps - may be controlled with the <em class="parameter"><code>timeout_usec</code></em> - parameter. Pass <code class="constant">(uint64_t) -1</code> to wait - indefinitely. Internally this call simply combines - <code class="function">sd_journal_get_fd()</code>, - <code class="function">sd_journal_get_events()</code>, - <code class="function">sd_journal_get_timeout()</code>, - <code class="function">poll()</code> and - <code class="function">sd_journal_process()</code> into one.</p><p><code class="function">sd_journal_reliable_fd()</code> may be used to - check whether the wakeup events from the file descriptor returned - by <code class="function">sd_journal_get_fd()</code> are known to be - immediately triggered. On certain file systems where file change - events from the OS are not available (such as NFS) changes need to - be polled for repeatedly, and hence are detected only with a - certain latency. This call will return a positive value if the - journal changes are detected immediately and zero when they need - to be polled for and hence might be noticed only with a certain - latency. Note that there's usually no need to invoke this function - directly as <code class="function">sd_journal_get_timeout()</code> on these - file systems will ask for timeouts explicitly anyway.</p></div><div class="refsect1"><a name="idm47966627368688"></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_fd()</code> returns a valid - file descriptor on success or a negative errno-style error - code.</p><p><code class="function">sd_journal_get_events()</code> returns a - combination of <code class="constant">POLLIN</code>, - <code class="constant">POLLOUT</code> and suchlike on success or a negative - errno-style error code.</p><p><code class="function">sd_journal_reliable_fd()</code> returns a - positive integer if the file descriptor returned by - <code class="function">sd_journal_get_fd()</code> will generate wake-ups - immediately for all journal changes. Returns 0 if there might be a - latency involved.</p><p><code class="function">sd_journal_process()</code> and - <code class="function">sd_journal_wait()</code> return one of - <code class="constant">SD_JOURNAL_NOP</code>, - <code class="constant">SD_JOURNAL_APPEND</code> or - <code class="constant">SD_JOURNAL_INVALIDATE</code> on success or a - negative errno-style error code. If - <code class="constant">SD_JOURNAL_NOP</code> is returned, the journal did - not change since the last invocation. If - <code class="constant">SD_JOURNAL_APPEND</code> is returned, new entries - have been appended to the end of the journal. If - <code class="constant">SD_JOURNAL_INVALIDATE</code>, journal files were - added or removed (possibly due to rotation). In the latter event, - live-view UIs should probably refresh their entire display, while - in the case of <code class="constant">SD_JOURNAL_APPEND</code>, it is - sufficient to simply continue reading at the previous end of the - journal.</p></div><div class="refsect1"><a name="idm47966625945536"></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_fd()</code>, - <code class="function">sd_journal_get_events()</code>, - <code class="function">sd_journal_reliable_fd()</code>, - <code class="function">sd_journal_process()</code> and - <code class="function">sd_journal_wait()</code> interfaces are available as - a shared library, which can be compiled and linked to with the - <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> - file.</p></div><div class="refsect1"><a name="idm47966627739136"></a><h2 id="Examples">Examples<a class="headerlink" title="Permalink to this headline" href="#Examples">¶</a></h2><p>Iterating through the journal, in a live view tracking all - changes:</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; - } - for (;;) { - const void *d; - size_t l; - r = sd_journal_next(j); - if (r < 0) { - fprintf(stderr, "Failed to iterate to next entry: %s\n", strerror(-r)); - break; - } - if (r == 0) { - /* Reached the end, let's wait for changes, and try again */ - r = sd_journal_wait(j, (uint64_t) -1); - if (r < 0) { - fprintf(stderr, "Failed to wait for changes: %s\n", strerror(-r)); - break; - } - continue; - } - 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, (const char*) d); - } - sd_journal_close(j); - return 0; -}</pre><p>Waiting with <code class="function">poll()</code> (this - example lacks all error checking for the sake of - simplicity):</p><pre class="programlisting">#include <poll.h> -#include <systemd/sd-journal.h> - -int wait_for_changes(sd_journal *j) { - struct pollfd pollfd; - int msec; - - sd_journal_get_timeout(m, &t); - if (t == (uint64_t) -1) - msec = -1; - else { - struct timespec ts; - uint64_t n; - clock_getttime(CLOCK_MONOTONIC, &ts); - n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000; - msec = t > n ? (int) ((t - n + 999) / 1000) : 0; - } - - pollfd.fd = sd_journal_get_fd(j); - pollfd.events = sd_journal_get_events(j); - poll(&pollfd, 1, msec); - return sd_journal_process(j); -}</pre></div><div class="refsect1"><a name="idm47966630650544"></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_next.html"><span class="citerefentry"><span class="refentrytitle">sd_journal_next</span>(3)</span></a>, - <a href="http://man7.org/linux/man-pages/man2/poll.2.html"><span class="citerefentry"><span class="refentrytitle">poll</span>(2)</span></a>, - <a href="http://man7.org/linux/man-pages/man2/clock_gettime.2.html"><span class="citerefentry"><span class="refentrytitle">clock_gettime</span>(2)</span></a> - </p></div></div></body></html> |