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- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id="sd_journal_next">
- <refentryinfo>
- <title>sd_journal_next</title>
- <productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
- </refentryinfo>
-
- <refmeta>
- <refentrytitle>sd_journal_next</refentrytitle>
- <manvolnum>3</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>sd_journal_next</refname>
- <refname>sd_journal_previous</refname>
- <refname>sd_journal_next_skip</refname>
- <refname>sd_journal_previous_skip</refname>
- <refname>SD_JOURNAL_FOREACH</refname>
- <refname>SD_JOURNAL_FOREACH_BACKWARDS</refname>
- <refpurpose>Advance or set back the read pointer in the journal</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_next</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_previous</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_next_skip</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>uint64_t <parameter>skip</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_previous_skip</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>uint64_t <parameter>skip</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef><function>SD_JOURNAL_FOREACH</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef><function>SD_JOURNAL_FOREACH_BACKWARDS</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para><function>sd_journal_next()</function> advances
- the read pointer into the journal by one entry. The
- only argument taken is a journal context object as
- allocated via
- <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>. After
- successful invocation the entry may be read with
- functions such as
- <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
-
- <para>Similarly, <function>sd_journal_previous()</function> sets
- the read pointer back one entry.</para>
-
- <para><function>sd_journal_next_skip()</function> and
- <function>sd_journal_previous_skip()</function>
- advance/set back the read pointer by multiple entries
- at once, as specified in the <varname>skip</varname>
- parameter.</para>
-
- <para>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.</para>
-
- <para>Note that
- <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- and related calls will fail unless
- <function>sd_journal_next()</function> has been
- invoked at least once in order to position the read
- pointer on a journal entry.</para>
-
- <para>Note that the
- <function>SD_JOURNAL_FOREACH()</function> macro may be used
- as a wrapper around
- <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- and <function>sd_journal_next()</function> in order to
- make iterating through the journal easier. See below
- for an example. Similarly,
- <function>SD_JOURNAL_FOREACH_BACKWARDS()</function>
- may be used for iterating the journal in reverse
- order.</para>
- </refsect1>
-
- <refsect1>
- <title>Return Value</title>
-
- <para>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
- <function>sd_journal_next()</function> or
- <function>sd_journal_previous()</function> 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.</para>
- </refsect1>
-
- <refsect1>
- <title>Notes</title>
-
- <para>The <function>sd_journal_next()</function>, <function>sd_journal_previous()</function>,
- <function>sd_journal_next_skip()</function> and
- <function>sd_journal_previous_skip()</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>
- file.</para>
- </refsect1>
-
- <refsect1>
- <title>Examples</title>
-
- <para>Iterating through the journal:</para>
-
- <programlisting>#include <stdio.h>
+ <refentryinfo>
+ <title>sd_journal_next</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>sd_journal_next</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_journal_next</refname>
+ <refname>sd_journal_previous</refname>
+ <refname>sd_journal_next_skip</refname>
+ <refname>sd_journal_previous_skip</refname>
+ <refname>SD_JOURNAL_FOREACH</refname>
+ <refname>SD_JOURNAL_FOREACH_BACKWARDS</refname>
+ <refpurpose>Advance or set back the read pointer in the journal</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_next</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_previous</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_next_skip</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>uint64_t <parameter>skip</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_previous_skip</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>uint64_t <parameter>skip</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef><function>SD_JOURNAL_FOREACH</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef><function>SD_JOURNAL_FOREACH_BACKWARDS</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_journal_next()</function> advances the read
+ pointer into the journal by one entry. The only argument taken is
+ a journal context object as allocated via
+ <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ After successful invocation the entry may be read with functions
+ such as
+ <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+ <para>Similarly, <function>sd_journal_previous()</function> sets
+ the read pointer back one entry.</para>
+
+ <para><function>sd_journal_next_skip()</function> and
+ <function>sd_journal_previous_skip()</function> advance/set back
+ the read pointer by multiple entries at once, as specified in the
+ <varname>skip</varname> parameter.</para>
+
+ <para>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.</para>
+
+ <para>Note that
+ <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ and related calls will fail unless
+ <function>sd_journal_next()</function> has been invoked at least
+ once in order to position the read pointer on a journal
+ entry.</para>
+
+ <para>Note that the <function>SD_JOURNAL_FOREACH()</function>
+ macro may be used as a wrapper around
+ <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ and <function>sd_journal_next()</function> in order to make
+ iterating through the journal easier. See below for an example.
+ Similarly, <function>SD_JOURNAL_FOREACH_BACKWARDS()</function> may
+ be used for iterating the journal in reverse order.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para>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
+ <function>sd_journal_next()</function> or
+ <function>sd_journal_previous()</function> 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.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>The <function>sd_journal_next()</function>,
+ <function>sd_journal_previous()</function>,
+ <function>sd_journal_next_skip()</function> and
+ <function>sd_journal_previous_skip()</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>
+ file.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <para>Iterating through the journal:</para>
+
+ <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", (const void **)&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;
+ 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", (const void **)&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;
}</programlisting>
- </refsect1>
+ </refsect1>
- <refsect1>
- <title>See Also</title>
+ <refsect1>
+ <title>See Also</title>
- <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_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- </para>
- </refsect1>
+ <para>
+ <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_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
</refentry>
~ianmdlvl / elogind.git / blobdiff