If <systemitem>csvlog</systemitem> is included in <varname>log_destination</varname>,
        log entries are output in <quote>comma-separated
        value</quote> (<acronym>CSV</acronym>) format, which is convenient for
        loading logs into programs.
        See <xref linkend="runtime-config-logging-csvlog"/> for details.
        <xref linkend="guc-logging-collector"/> must be enabled to generate
        CSV-format log output.
       </para>
       <para>
        If <systemitem>jsonlog</systemitem> is included in
        <varname>log_destination</varname>, log entries are output in
        <acronym>JSON</acronym> format, which is convenient for loading logs
        into programs.
        See <xref linkend="runtime-config-logging-jsonlog"/> for details.
        <xref linkend="guc-logging-collector"/> must be enabled to generate
        JSON-format log output.
       </para>
       <para>
        When either <systemitem>stderr</systemitem>,
        <systemitem>csvlog</systemitem> or <systemitem>jsonlog</systemitem> are
        included, the file <filename>current_logfiles</filename> is created to
        record the location of the log file(s) currently in use by the logging
        collector and the associated logging destination. This provides a
        convenient way to find the logs currently in use by the instance. Here
        is an example of this file's content:
<programlisting>
stderr log/postgresql.log
csvlog log/postgresql.csv
jsonlog log/postgresql.json
</programlisting>

        <filename>current_logfiles</filename> is recreated when a new log file
        is created as an effect of rotation, and
        when <varname>log_destination</varname> is reloaded.  It is removed when
        none of <systemitem>stderr</systemitem>,
        <systemitem>csvlog</systemitem> or <systemitem>jsonlog</systemitem> are
        included in <varname>log_destination</varname>, and when the logging
        collector is disabled.
       </para>

       <note>
        <para>
         On most Unix systems, you will need to alter the configuration of
         your system's <application>syslog</application> daemon in order
         to make use of the <systemitem>syslog</systemitem> option for
         <varname>log_destination</varname>.  <productname>PostgreSQL</productname>
         can log to <application>syslog</application> facilities
         <literal>LOCAL0</literal> through <literal>LOCAL7</literal> (see <xref
         linkend="guc-syslog-facility"/>), but the default
         <application>syslog</application> configuration on most platforms
         will discard all such messages.  You will need to add something like:
<programlisting>
local0.*    /var/log/postgresql
</programlisting>
         to the  <application>syslog</application> daemon's configuration file
         to make it work.
        </para>
        <para>
         On Windows, when you use the <literal>eventlog</literal>
         option for <varname>log_destination</varname>, you should
         register an event source and its library with the operating
         system so that the Windows Event Viewer can display event
         log messages cleanly.
         See <xref linkend="event-log-registration"/> for details.
        </para>
       </note>
      </listitem>
     </varlistentry>

     <varlistentry id="guc-logging-collector" xreflabel="logging_collector">
      <term><varname>logging_collector</varname> (<type>boolean</type>)
      <indexterm>
       <primary><varname>logging_collector</varname> configuration parameter</primary>
      </indexterm>
      </term>
      <listitem>
       <para>
         This parameter enables the <firstterm>logging collector</firstterm>, which
         is a background process that captures log messages
         sent to <systemitem>stderr</systemitem> and redirects them into log files.
         This approach is often more useful than
         logging to <application>syslog</application>, since some types of messages
         might