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diff --git a/man/sd_journal_next.xml b/man/sd_journal_next.xml new file mode 100644 index 0000000000..f55ee15744 --- /dev/null +++ b/man/sd_journal_next.xml @@ -0,0 +1,194 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + This file is part of systemd. + + Copyright 2012 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +--> + +<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> + <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> + + </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>Similar, <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 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 iteratring through the journal easier. See below + for an example. Similar, + <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 (resp. 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 shared library, which can be compiled and + linked to with the + <literal>libsystemd-journal</literal> + <citerefentry><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", &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> + <title>See Also</title> + + <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> + </para> + </refsect1> + +</refentry> |