man: document sd_journal_next()
This commit is contained in:
Lennart Poettering
parent
3bb55eee6a
commit
67c3cf4f9e
11
Makefile.am
11
Makefile.am
|
|
@ -501,7 +501,8 @@ MANPAGES = \
|
|||
man/sd-journal.3 \
|
||||
man/sd_journal_print.3 \
|
||||
man/sd_journal_stream_fd.3 \
|
||||
man/sd_journal_open.3
|
||||
man/sd_journal_open.3 \
|
||||
man/sd_journal_next.3
|
||||
|
||||
MANPAGES_ALIAS = \
|
||||
man/reboot.8 \
|
||||
|
|
@ -543,7 +544,10 @@ MANPAGES_ALIAS = \
|
|||
man/sd_journal_send.3 \
|
||||
man/sd_journal_sendv.3 \
|
||||
man/sd_journal_open_directory.3 \
|
||||
man/sd_journal_close.3
|
||||
man/sd_journal_close.3 \
|
||||
man/sd_journal_previous.3 \
|
||||
man/sd_journal_next_skip.3 \
|
||||
man/sd_journal_previous_skip.3
|
||||
|
||||
man/reboot.8: man/halt.8
|
||||
man/poweroff.8: man/halt.8
|
||||
|
|
@ -585,6 +589,9 @@ man/sd_journal_send.3: man/sd_journal_print.3
|
|||
man/sd_journal_sendv.3: man/sd_journal_print.3
|
||||
man/sd_journal_open_directory.3: man/sd_journal_open.3
|
||||
man/sd_journal_close.3: man/sd_journal_open.3
|
||||
man/sd_journal_previous.3: man/sd_journal_next.3
|
||||
man/sd_journal_next_skip.3: man/sd_journal_next.3
|
||||
man/sd_journal_previous_skip.3: man/sd_journal_next.3
|
||||
|
||||
XML_FILES = \
|
||||
${patsubst %.1,%.xml,${patsubst %.3,%.xml,${patsubst %.5,%.xml,${patsubst %.7,%.xml,${patsubst %.8,%.xml,$(MANPAGES)}}}}}
|
||||
|
|
|
|||
|
|
@ -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>
|
||||
|
|
@ -89,7 +89,7 @@
|
|||
be opened. <literal>SD_JOURNAL_RUNTIME_ONLY</literal>
|
||||
makes sure only volatile journal files will be opened,
|
||||
excluding those which are stored on persistant
|
||||
storage. <literal>SD_JOURNAL_RUNTIME_ONLY</literal>
|
||||
storage. <literal>SD_JOURNAL_SYSTEM_ONLY</literal>
|
||||
will ensure that only journal files of system services
|
||||
and the kernel (in opposition to user session processes) will
|
||||
be opened.</para>
|
||||
|
|
@ -112,6 +112,12 @@
|
|||
accessible to the calling user will be opened. If
|
||||
journal files are not accessible to the caller this
|
||||
will be silently ignored.</para>
|
||||
|
||||
<para>See
|
||||
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||||
for an example how to iterate through the journal
|
||||
after opening it it with
|
||||
<function>sd_journal_open()</function>.</para>
|
||||
</refsect1>
|
||||
|
||||
<refsect1>
|
||||
|
|
|
|||
|
|
@ -127,6 +127,8 @@
|
|||
|
||||
<programlisting>#include <syslog.h>
|
||||
#include <stdio.h>
|
||||
#include <string.h>
|
||||
#include <unistd.h>
|
||||
#include <systemd/sd-journal.h>
|
||||
#include <systemd/sd-daemon.h>
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue