mirror of
https://github.com/AuxXxilium/eudev.git
synced 2024-12-24 02:20:45 +07:00
215 lines
9.5 KiB
XML
215 lines
9.5 KiB
XML
<?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>
|
|
<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>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
|
|
<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 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>,
|
|
<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>
|