diff options
| -rw-r--r-- | man/sd_journal_get_fd.xml | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/man/sd_journal_get_fd.xml b/man/sd_journal_get_fd.xml new file mode 100644 index 0000000000..f4db2a392a --- /dev/null +++ b/man/sd_journal_get_fd.xml @@ -0,0 +1,160 @@ +<?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_get_fd"> + + <refentryinfo> + <title>sd_journal_get_fd</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_get_fd</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_journal_get_fd</refname> + <refname>sd_journal_get_process</refname> + <refname>sd_journal_get_wait</refname> + <refpurpose>Journal change notification + interface</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> + + <funcprototype> + <funcdef>int <function>sd_journal_get_fd</function></funcdef> + <paramdef>sd_journal* <parameter>j</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_journal_process</function></funcdef> + <paramdef>sd_journal* <parameter>j</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_journal_wait</function></funcdef> + <paramdef>sd_journal* <parameter>j</parameter></paramdef> + <paramdef>uint64_t <parameter>timeout_usec</parameter></paramdef> + </funcprototype> + + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><function>sd_journal_get_fd()</function> returns + a file descriptor that may be asynchronously polled in + an external event loop and is signalled readable as + soon as the journal changes, for example because new + entries were added. The file descriptor is suitable + for usage in + <citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry> + where it will yield POLLIN on all changes. The call + takes one argument: the journal context object.</para> + + <para>After each POLLIN wake-up + <function>sd_journal_process()</function> needs to be + called to process events and reset the readable state + of the file descriptor. This call will also indicate + what kind of change has been detected (see below; note + that spurious wake-ups are possible).</para> + + <para>A synchronous alternative for using + <function>sd_journal_get_fd()</function> and + <function>sd_journal_process()</function> is + <function>sd_journal_wait()</function>. It will + synchronously wait until the journal gets changed up + to a certain time-out as specified in its second + argument. Pass <literal>(uint64_t) -1</literal> to + wait indefinitely. Internally this call simply + combines <function>sd_journal_get_fd()</function>, + <function>poll()</function> and + <function>sd_journal_process()</function> into + one.</para> + + </refsect1> + + <refsect1> + <title>Return Value</title> + + <para><function>sd_journal_get_fd()</function> returns a valid file descriptor on success or a negative errno-style error + code.</para> + + <para><function>sd_journal_process()</function> and + <function>sd_journal_wait()</function> return one of + <literal>SD_JOURNAL_NOP</literal>, + <literal>SD_JOURNAL_APPEND</literal> or + <literal>SD_JOURNAL_INVALIDATE</literal> on success or + a negative errno-style error code. If + <literal>SD_JOURNAL_NOP</literal> is returned the + journal didn't change since the last invocation. If + <literal>SD_JOURNAL_APPEND</literal> is returned new + entries have been appended to the end of the + journal. If <literal>SD_JOURNAL_INVALIDATE</literal> + 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 <literal>SD_JOURNAL_APPEND</literal> it is + sufficient to simply continue reading at the previous + end of the journal.</para> + </refsect1> + + <refsect1> + <title>Notes</title> + + <para>The <function>sd_journal_get_fd()</function>, + <function>sd_journal_process()</function> and + <function>sd_journal_wait()</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>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_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |