protocol.xml

<?xml version='1.0' encoding="utf-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
                      "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">

<book>
  <title>The Music Player Daemon protocol</title>

  <chapter id="syntax">
    <title>General protocol syntax</title>

    <section>
      <title>Protocol overview</title>

      <para>
        The <application>MPD</application> command protocol exchanges
        line-based text records between client and server over TCP.
        Once the client is connected to the server, they conduct a
        conversation until the client closes the connection. The
        conversation flow is always initiated by the client.
      </para>

      <para>
        The client transmits a command sequence, terminated by the
        newline character <constant>\n</constant>.  The server will
        respond with one or more lines, the last of which will be a
        completion code.
      </para>

      <para>
        When the client connects to the server, the server will answer
        with the following line:

        <synopsis>OK MPD version</synopsis>

        where <varname>version</varname> is a version identifier such as
        0.12.2.  This version identifier is the version of the protocol
        spoken, not the real version of the daemon.  (There is no way to
        retrieve this real version identifier from the connection.)
      </para>
    </section>

    <section id="request_syntax">
      <title>Requests</title>

      <cmdsynopsis>
        <command>COMMAND</command>
        <arg rep="repeat"><replaceable>ARG</replaceable></arg>
      </cmdsynopsis>

      <para>
        If arguments contain spaces, they should be surrounded by double
        quotation marks.
      </para>

      <para>
        Argument strings are separated from the command and any other
        arguments by linear white-space (' ' or '\t').
      </para>

      <para>
        All data between the client and the server is encoded in
        UTF-8.
      </para>
    </section>

    <section id="response_syntax">
      <title>Responses</title>

      <para>
        A command returns <returnvalue>OK</returnvalue> on completion or
        <returnvalue>ACK some error</returnvalue> on failure.  These
        denote the end of command execution.
      </para>

      <section id="failure_response_syntax">
        <title>Failure responses</title>

        <para>
          The nature of the error can be gleaned from the information
          that follows the <returnvalue>ACK</returnvalue>.
          <returnvalue>ACK</returnvalue> lines are of the form:

          <synopsis>ACK [error@command_listNum] {current_command} message_text\n</synopsis>

          These responses are generated by a call to
          <function>commandError</function>. They contain four separate
          terms. Let's look at each of them:

          <itemizedlist>
            <listitem>
              <para>
                <returnvalue>error</returnvalue>: numeric value of one
                of the <constant>ACK_ERROR</constant> constants defined
                in <filename>src/protocol/Ack.hxx</filename>.
              </para>
            </listitem>
            <listitem>
              <para>
                <returnvalue>command_listNum</returnvalue>:
                offset of the command that caused the error in a <link
                  linkend="command_lists">Command List</link>.
                An error will always cause a command list to terminate
                at the command that causes the error.
              </para>
            </listitem>
            <listitem>
              <para>
                <returnvalue>current_command</returnvalue>:
                name of the command, in a <link
                  linkend="command_lists">Command List</link>,
                that was executing when the error occurred.
              </para>
            </listitem>
            <listitem>
              <para>
                <returnvalue>message_text</returnvalue>:
                some (hopefully) informative text that describes the
                nature of the error.
              </para>
            </listitem>
          </itemizedlist>
        </para>

        <example>
          <title>foo</title>
          <para>
            An example might help. Consider the following sequence
            sent from the client to the server.

            <synopsis>
              command_list_begin
              volume 86
              play 10240
              status
              command_list_end
            </synopsis>
          </para>

          <para>
            The server responds with:

            <returnvalue>
              ACK [50@1] {play} song doesn't exist: "10240"
            </returnvalue>
          </para>

          <para>
            This tells us that the play command, which was the
            second in the list (the first or only command is
            numbered 0), failed with error 50.  The number 50
            translates to <constant>ACK_ERROR_NO_EXIST</constant>--the
            song doesn't exist.  This is reiterated by the message text
            which also tells us which song doesn't exist.
          </para>

        </example>
      </section>
    </section>

    <section id="command_lists">
      <title>Command lists</title>

      <para>
        To facilitate faster adding of files etc. you can pass a list
        of commands all at once using a command list.  The command
        list begins with <command>command_list_begin</command> or
        <command>command_list_ok_begin</command> and ends with
        <command>command_list_end</command>.
      </para>

      <para>
        It does not execute any commands until the list has ended.
        The return value is whatever the return for a list of commands
        is.  On success for all commands,
        <returnvalue>OK</returnvalue> is returned.  If a command
        fails, no more commands are executed and the appropriate
        <returnvalue>ACK</returnvalue> error is returned. If
        <command>command_list_ok_begin</command> is used,
        <returnvalue>list_OK</returnvalue> is returned for each
        successful command executed in the command list.
      </para>
    </section>

    <section id="range_syntax">
      <title>Ranges</title>

      <para>
        Some commands (e.g. <link
        linkend="command_delete"><command>delete</command></link>)
        allow specifying a range in the form
        <parameter>START:END</parameter> (the <varname>END</varname>
        item is not included in the range, similar to ranges in the
        Python programming language).  If <varname>END</varname> is
        omitted, then the maximum possible value is assumed.
      </para>
    </section>

    <section id="filter_syntax">
      <title>Filters</title>

      <para>
        All commands which search for songs (e.g. <link
        linkend="command_find"><command>find</command></link> and
        <link
        linkend="command_searchadd"><command>searchadd</command></link>)
        share a common filter syntax:
      </para>

      <cmdsynopsis>
        <command>find</command>
        <arg choice="req" rep="repeat">EXPRESSION</arg>
      </cmdsynopsis>

      <para>
        <varname>EXPRESSION</varname> is a string enclosed in
        parantheses which can be one of:
      </para>

      <itemizedlist>
        <listitem>
          <para>
            "<code>(TAG == 'VALUE')</code>": match a tag value.
          </para>

          <para>
            "<code>(TAG != 'VALUE')</code>": mismatch a tag value.
          </para>

          <para>
            The special tag "<parameter>any</parameter>" checks all
            tag values.
          </para>

          <para>
            <parameter>albumartist</parameter> looks for
            <varname>VALUE</varname> in <varname>AlbumArtist</varname>
            and falls back to <varname>Artist</varname> tags if
            <varname>AlbumArtist</varname> does not exist.
          </para>

          <para>
            <varname>VALUE</varname> is what to find.  The
            <command>find</command> commands specify an exact value
            and are case-sensitive; the <command>search</command>
            commands specify a sub string and ignore case.
          </para>
        </listitem>

        <listitem>
          <para>
            "<code>(file == 'VALUE')</code>": match the full song URI
            (relative to the music directory).
          </para>
        </listitem>

        <listitem>
          <para>
            "<code>(base 'VALUE')</code>": restrict the search to
            songs in the given directory (relative to the music
            directory).
          </para>
        </listitem>

        <listitem>
          <para>
            "<code>(modified-since 'VALUE')</code>": compares the
            file's time stamp with the given value (ISO 8601 or UNIX
            time stamp).
          </para>
        </listitem>

        <listitem>
          <para>
            "<code>(AudioFormat == 'SAMPLERATE:BITS:CHANNELS')</code>":
            compares the audio format with the given value.
          </para>
        </listitem>

        <listitem>
          <para>
            "<code>(AudioFormat =~ 'SAMPLERATE:BITS:CHANNELS')</code>":
            matches the audio format with the given mask (i.e. one
            or more attributes may be "<code>*</code>").
          </para>
        </listitem>

        <listitem>
          <para>
            "<code>(!EXPRESSION)</code>": negate an expression.
          </para>
        </listitem>

        <listitem>
          <para>
            "<code>(EXPRESSION1 AND EXPRESSION2 ...)</code>": combine two or
            more expressions with logical "and".
          </para>
        </listitem>
      </itemizedlist>

      <para>
        Prior to MPD 0.21, the syntax looked like this:
      </para>

      <cmdsynopsis>
        <command>find</command>
        <arg choice="req" rep="repeat">
          <arg choice="req"><replaceable>TYPE</replaceable></arg>
          <arg choice="req"><replaceable>VALUE</replaceable></arg>
        </arg>
      </cmdsynopsis>
    </section>

    <section id="tags">
      <title>Tags</title>

      <para>
        The following tags are supported by
        <application>MPD</application>:
      </para>

      <xi:include href="include/tags.xml"
                  xmlns:xi="http://www.w3.org/2001/XInclude"/>

      <para>
        There can be multiple values for some of these tags.  For
        example, <application>MPD</application> may return multiple
        lines with a <varname>performer</varname> tag.  A tag value is
        a UTF-8 string.
      </para>
    </section>

    <section id="other_metadata">
      <title>Other Metadata</title>

      <para>
        The response to <link
        linkend="command_lsinfo"><command>lsinfo</command></link> and
        similar commands may contain <link linkend="tags">song
        tags</link> and other metadata, specifically:
      </para>

      <itemizedlist>
        <listitem>
          <para>
            <varname>duration</varname>: the duration of the song in
            seconds; may contain a fractional part.
          </para>
        </listitem>

        <listitem>
          <para>
            <varname>time</varname>: like <varname>duration</varname>,
            but as integer value.  This is deprecated and is only here
            for compatibility with older clients.  Do not use.
          </para>
        </listitem>

        <listitem>
          <para>
            <varname>Range</varname>: if this is a queue item
            referring only to a portion of the song file, then this
            attribute contains the time range in the form
            <parameter>START-END</parameter> or
            <parameter>START-</parameter> (open ended); both
            <parameter>START</parameter> and
            <parameter>END</parameter> are time stamps within the song
            in seconds (may contain a fractional part).  Example:
            "<parameter>60-120</parameter>" plays only the second
            minute; "<parameter>180</parameter>" skips the first three
            minutes.
          </para>
        </listitem>

        <listitem>
          <para>
            <varname>Format</varname>: the audio format of the song
            (or an approximation to a format supported by MPD and the
            decoder plugin being used).  When playing this file, the
            <varname>audio</varname> value in the <link
            linkend="command_status"><command>status</command></link>
            response should be the same.
          </para>
        </listitem>

        <listitem>
          <para>
            <varname>Last-Modified</varname>: the time stamp of the
            last modification of the underlying file in ISO 8601
            format.  Example:
            "<parameter>2008-09-28T20:04:57Z</parameter>"
          </para>
        </listitem>
      </itemizedlist>
    </section>
  </chapter>

  <chapter id="recipes">
    <title>Recipes</title>

    <section id="queuing_recipe">
      <title>Queuing</title>

      <para>
        Often, users run <application>MPD</application> with "<link
        linkend="command_random">random</link>" enabled, but want to
        be able to insert songs "before" the rest of the playlist.
        That is commonly called "queuing".
      </para>

      <para>
        <application>MPD</application> implements this by allowing the client to specify a
        "priority" for each song in the playlist (commands <link
        linkend="command_prio"><command>prio</command></link> and
        <link
        linkend="command_prioid"><command>prioid</command></link>).  A
        higher priority means that the song is going to be played
        before the other songs.
      </para>

      <para>
        In "random" mode, <application>MPD</application> maintains an
        internal randomized sequence of songs.  In this sequence,
        songs with a higher priority come first, and all songs with
        the same priority are shuffled (by default, all songs are
        shuffled, because all have the same priority "0").  When you
        increase the priority of a song, it is moved to the front of
        the sequence according to its new priority, but always after
        the current one.  A song that has been played already (it's
        "before" the current song in that sequence) will only be
        scheduled for repeated playback if its priority has become
        bigger than the priority of the current song.  Decreasing the
        priority of a song will move it farther to the end of the
        sequence.  Changing the priority of the current song has no
        effect on the sequence.  During playback, a song's priority is
        reset to zero.
      </para>
    </section>
  </chapter>

  <chapter id="command_reference">
    <title>Command reference</title>

    <note>
      <para>
        For manipulating playlists and playing, there are two sets of
        commands.  One set uses the song id of a song in the playlist,
        while another set uses the playlist position of the song. The
        commands using song ids should be used instead of the commands
        that manipulate and control playback based on playlist
        position. Using song ids is a safer method when multiple
        clients are interacting with <application>MPD</application>.
      </para>
    </note>

    <section id="status_commands">
      <title>Querying <application>MPD</application>'s status</title>

      <variablelist>
        <varlistentry id="command_clearerror">
          <term>
            <cmdsynopsis>
              <command>clearerror</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Clears the current error message in status (this is also
              accomplished by any command that starts playback).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_currentsong">
          <term>
            <cmdsynopsis>
              <command>currentsong</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Displays the song info of the current song (same song that
              is identified in status).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_idle">
          <term>
            <cmdsynopsis>
              <command>idle</command>
              <arg choice="opt" rep="repeat"><replaceable>SUBSYSTEMS</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              <footnote id="since_0_14"><simpara>Introduced with
              <application>MPD</application> 0.14</simpara></footnote>
              Waits until there is a noteworthy change in one or more
              of <application>MPD</application>'s subsystems.  As soon
              as there is one, it lists all changed systems in a line
              in the format <returnvalue>changed:
              SUBSYSTEM</returnvalue>, where SUBSYSTEM is one of the
              following:
            </para>
            <itemizedlist>
              <listitem>
                <para>
                  <returnvalue>database</returnvalue>: the song
                  database has been modified after <link
                  linkend="command_update"><command>update</command></link>.
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>update</returnvalue>: a database update
                  has started or finished.  If the database was
                  modified during the update, the
                  <returnvalue>database</returnvalue> event is also
                  emitted.
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>stored_playlist</returnvalue>: a stored
                  playlist has been modified, renamed, created or
                  deleted
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>playlist</returnvalue>: the current
                  playlist has been modified
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>player</returnvalue>: the player has been
                  started, stopped or seeked
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>mixer</returnvalue>: the volume has been
                  changed
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>output</returnvalue>: an audio output
                  has been added, removed or modified (e.g. renamed,
                  enabled or disabled)
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>options</returnvalue>: options like
                  <option>repeat</option>, <option>random</option>,
                  <option>crossfade</option>, replay gain
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>partition</returnvalue>: a partition
                  was added, removed or changed
                </para>
              </listitem>
              <listitem>
                <para>
                    <returnvalue>sticker</returnvalue>: the sticker database
                    has been modified.
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>subscription</returnvalue>: a client
                  has subscribed or unsubscribed to a channel
                </para>
              </listitem>
              <listitem>
                <para>
                  <returnvalue>message</returnvalue>: a message was
                  received on a channel this client is subscribed to;
                  this event is only emitted when the queue is empty
                </para>
              </listitem>
            </itemizedlist>

            <para>
              Change events accumulate, even while the connection is
              not in "idle" mode; no events gets lost while the client
              is doing something else with the connection.  If an
              event had already occurred since the last call, the new
              <link
              linkend="command_idle"><command>idle</command></link>
              command will return immediately.
            </para>

            <para>
              While a client is waiting for <command>idle</command>
              results, the server disables timeouts, allowing a client
              to wait for events as long as mpd runs.  The
              <command>idle</command> command can be canceled by
              sending the command <command>noidle</command> (no other
              commands are allowed). <application>MPD</application>
              will then leave <command>idle</command> mode and print
              results immediately; might be empty at this time.
            </para>
            <para>
              If the optional <varname>SUBSYSTEMS</varname> argument
              is used, <application>MPD</application> will only send
              notifications when something changed in one of the
              specified subsytems.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_status">
          <term>
            <cmdsynopsis>
              <command>status</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Reports the current status of the player and the volume
              level.
            </para>
            <itemizedlist>
              <listitem>
                <para>
                  <varname>volume</varname>:
                  <returnvalue>0-100</returnvalue> or
                  <returnvalue>-1</returnvalue> if the volume cannot
                  be determined
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>repeat</varname>:
                  <returnvalue>0 or 1</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>random</varname>:
                  <returnvalue>0 or 1</returnvalue>
                </para>
              </listitem>
              <listitem>
               <para>
                <varname>single</varname>:
                <footnote id="since_0_15"><simpara>Introduced with <application>MPD</application> 0.15 (oneshot introduced with 0.20)</simpara></footnote>
                <returnvalue>0, 1, or oneshot</returnvalue>
               </para>
              </listitem>
              <listitem>
               <para>
                <varname>consume</varname>:
                <footnoteref linkend="since_0_15"/>
                <returnvalue>0 or 1</returnvalue>
               </para>
              </listitem>
              <listitem>
                <para>
                  <varname>playlist</varname>:
                  <returnvalue>31-bit unsigned integer, the playlist
                  version number</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>playlistlength</varname>:
                  <returnvalue>integer, the length of the
                  playlist</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>state</varname>:
                  <returnvalue>play, stop, or pause</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>song</varname>:
                  <returnvalue> playlist song number of the current
                  song stopped on or playing
                  </returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>songid</varname>:
                  <returnvalue>playlist songid of the current song
                  stopped on or playing
                  </returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>nextsong</varname>:
                  <footnoteref linkend="since_0_15"/>
                  <returnvalue> playlist song number of the next
                  song to be played
                  </returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>nextsongid</varname>:
                  <footnoteref linkend="since_0_15"/>
                  <returnvalue>playlist songid of the next song
                  to be played
                  </returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>time</varname>:
                  <returnvalue>total time elapsed (of current
                  playing/paused song)</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>elapsed</varname>:
                  <footnote id="since_0_16"><simpara>Introduced with <application>MPD</application> 0.16</simpara></footnote>
                  <returnvalue>
                    Total time elapsed within the current song, but
                    with higher resolution.
                  </returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>duration</varname>:
                  <footnote id="since_0_20"><simpara>Introduced with <application>MPD</application> 0.20</simpara></footnote>
                  <returnvalue>
                    Duration of the current song in seconds.
                  </returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>bitrate</varname>:
                  <returnvalue>instantaneous bitrate in
                  kbps</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>xfade</varname>:
                  <returnvalue>crossfade in seconds</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>mixrampdb</varname>:
                  <returnvalue>mixramp threshold in dB</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>mixrampdelay</varname>:
                  <returnvalue>mixrampdelay in seconds</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>audio</varname>:
                  <returnvalue>
                    The format emitted by the decoder plugin during
                    playback, format:
                    "<replaceable>samplerate:bits:channels</replaceable>".
                    Check the user manual for a detailed explanation.
                  </returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>updating_db</varname>:
                  <returnvalue>job id</returnvalue>
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>error</varname>:
                  <returnvalue>if there is an error, returns message
                  here</returnvalue>
                </para>
                </listitem>
            </itemizedlist>
          </listitem>
        </varlistentry>
        <varlistentry id="command_stats">
          <term>
            <cmdsynopsis>
              <command>stats</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Displays statistics.
            </para>
            <itemizedlist>
              <listitem>
                <para>
                  <varname>artists</varname>: number of artists
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>albums</varname>: number of albums
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>songs</varname>: number of songs
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>uptime</varname>: daemon uptime in seconds
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>db_playtime</varname>: sum of all song
                  times in the db
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>db_update</varname>: last db update in UNIX
                  time
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>playtime</varname>: time length of music played
                </para>
              </listitem>
            </itemizedlist>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="playback_option_commands">
      <title>Playback options</title>

      <variablelist>
        <varlistentry id="command_consume">
          <term>
            <cmdsynopsis>
              <command>consume</command>
              <arg choice="req"><replaceable>STATE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              <footnoteref linkend="since_0_15"/>
              Sets consume state to <varname>STATE</varname>,
              <varname>STATE</varname> should be 0 or 1.
	      When consume is activated, each song played is removed from playlist.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_crossfade">
          <term>
            <cmdsynopsis>
              <command>crossfade</command>
              <arg choice="req"><replaceable>SECONDS</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Sets crossfading between songs.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_mixrampdb">
          <term>
            <cmdsynopsis>
              <command>mixrampdb</command>
              <arg choice="req"><replaceable>deciBels</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Sets the threshold at which songs will be overlapped. Like crossfading but doesn't fade the track volume, just overlaps. The songs need to have MixRamp tags added by an external tool. 0dB is the normalized maximum volume so use negative values, I prefer -17dB. In the absence of mixramp tags crossfading will be used. See http://sourceforge.net/projects/mixramp
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_mixrampdelay">
          <term>
            <cmdsynopsis>
              <command>mixrampdelay</command>
              <arg choice="req"><replaceable>SECONDS</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Additional time subtracted from the overlap calculated by mixrampdb. A value of "nan" disables MixRamp overlapping and falls back to crossfading.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_random">
          <term>
            <cmdsynopsis>
              <command>random</command>
              <arg choice="req"><replaceable>STATE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Sets random state to <varname>STATE</varname>,
              <varname>STATE</varname> should be 0 or 1.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_repeat">
          <term>
            <cmdsynopsis>
              <command>repeat</command>
              <arg choice="req"><replaceable>STATE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Sets repeat state to <varname>STATE</varname>,
              <varname>STATE</varname> should be 0 or 1.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_setvol">
          <term>
            <cmdsynopsis>
              <command>setvol</command>
              <arg choice="req"><replaceable>VOL</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Sets volume to <varname>VOL</varname>, the range of
              volume is 0-100.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_single">
          <term>
            <cmdsynopsis>
              <command>single</command>
              <arg choice="req"><replaceable>STATE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              <footnoteref linkend="since_0_15"/>
              Sets single state to <varname>STATE</varname>,
              <varname>STATE</varname> should be 0 or 1.
	      When single is activated, playback is stopped after current song, or
	      song is repeated if the 'repeat' mode is enabled.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_replay_gain_mode">
          <term>
            <cmdsynopsis>
              <command>replay_gain_mode</command>
              <arg choice="req"><replaceable>MODE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Sets the replay gain mode.  One of
              <parameter>off</parameter>,
              <parameter>track</parameter>,
              <parameter>album</parameter>,
              <parameter>auto</parameter><footnote
                        id="replay_gain_auto_since_0_16">
                <simpara>added in <application>MPD</application> 0.16</simpara>
              </footnote>.
            </para>
            <para>
              Changing the mode during playback may take several
              seconds, because the new settings does not affect the
              buffered data.
            </para>
            <para>
              This command triggers the
              <returnvalue>options</returnvalue> idle event.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_replay_gain_status">
          <term>
            <cmdsynopsis>
              <command>replay_gain_status</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Prints replay gain options.  Currently, only the
              variable <varname>replay_gain_mode</varname> is
              returned.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_volume">
          <term>
            <cmdsynopsis>
              <command>volume</command>
              <arg choice="req"><replaceable>CHANGE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Changes volume by amount <varname>CHANGE</varname>.
            </para>
            <note>
              <para>
                <command>volume</command> is deprecated, use <link
                linkend="command_setvol"><command>setvol</command></link>
                instead.
              </para>
            </note>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="playback_commands">
      <title>Controlling playback</title>

      <variablelist>
        <varlistentry id="command_next">
          <term>
            <cmdsynopsis>
              <command>next</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Plays next song in the playlist.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_pause">
          <term>
            <cmdsynopsis>
              <command>pause</command>
              <arg choice="req"><replaceable>PAUSE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Toggles pause/resumes playing, <varname>PAUSE</varname> is 0 or 1.
            </para>
            <note>
              <para>
                The use of pause command w/o the PAUSE argument is
                deprecated.
              </para>
            </note>
          </listitem>
        </varlistentry>
        <varlistentry id="command_play">
          <term>
            <cmdsynopsis>
              <command>play</command>
              <arg><replaceable>SONGPOS</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Begins playing the playlist at song number
              <varname>SONGPOS</varname>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playid">
          <term>
            <cmdsynopsis>
              <command>playid</command>
              <arg><replaceable>SONGID</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Begins playing the playlist at song
              <varname>SONGID</varname>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_previous">
          <term>
            <cmdsynopsis>
              <command>previous</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Plays previous song in the playlist.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_seek">
          <term>
            <cmdsynopsis>
              <command>seek</command>
              <arg choice="req"><replaceable>SONGPOS</replaceable></arg>
              <arg choice="req"><replaceable>TIME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Seeks to the position <varname>TIME</varname> (in
              seconds; fractions allowed) of entry
              <varname>SONGPOS</varname> in the playlist.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_seekid">
          <term>
            <cmdsynopsis>
              <command>seekid</command>
              <arg choice="req"><replaceable>SONGID</replaceable></arg>
              <arg choice="req"><replaceable>TIME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Seeks to the position <varname>TIME</varname> (in
              seconds; fractions allowed) of song
              <varname>SONGID</varname>.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_seekcur">
          <term>
            <cmdsynopsis>
              <command>seekcur</command>
              <arg choice="req"><replaceable>TIME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Seeks to the position <varname>TIME</varname> (in
              seconds; fractions allowed) within the current song.  If
              prefixed by '+' or '-', then the time is relative to the
              current playing position.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_stop">
          <term>
            <cmdsynopsis>
              <command>stop</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Stops playing.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="queue">
      <title>The current playlist</title>

      <variablelist>
        <varlistentry id="command_add">
          <term>
            <cmdsynopsis>
              <command>add</command>
              <arg choice="req"><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Adds the file <varname>URI</varname> to the playlist
              (directories add recursively). <varname>URI</varname>
              can also be a single file.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_addid">
          <term>
            <cmdsynopsis>
              <command>addid</command>
              <arg choice="req"><replaceable>URI</replaceable></arg>
              <arg><replaceable>POSITION</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Adds a song to the playlist (non-recursive) and returns the song id.
            </para>
            <para>
              <varname>URI</varname> is always a single file or
              URL.  For example:
            </para>
            <screen>
addid "foo.mp3"
Id: 999
OK
            </screen>
          </listitem>
        </varlistentry>
        <varlistentry id="command_clear">
          <term>
            <cmdsynopsis>
              <command>clear</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Clears the current playlist.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_delete">
          <term>
            <cmdsynopsis>
              <command>delete</command>
              <group>
                <arg choice="req"><replaceable>POS</replaceable></arg>
                <arg choice="req"><replaceable>START:END</replaceable></arg>
              </group>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Deletes a song from the playlist.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_deleteid">
          <term>
            <cmdsynopsis>
              <command>deleteid</command>
              <arg choice="req"><replaceable>SONGID</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Deletes the song <varname>SONGID</varname> from the
              playlist
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_move">
          <term>
            <cmdsynopsis>
              <command>move</command>
              <group>
                  <arg choice="req"><replaceable>FROM</replaceable></arg>
                  <arg choice="req"><replaceable>START:END</replaceable></arg>
              </group>
              <arg choice="req"><replaceable>TO</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Moves the song at <varname>FROM</varname> or range of songs
              at <varname>START:END</varname> to <varname>TO</varname>
              in the playlist.
              <footnote id="range_since_0_15">
                <simpara>Ranges are supported since <application>MPD</application> 0.15</simpara>
              </footnote>
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_moveid">
          <term>
            <cmdsynopsis>
              <command>moveid</command>
              <arg choice="req"><replaceable>FROM</replaceable></arg>
              <arg choice="req"><replaceable>TO</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Moves the song with <varname>FROM</varname> (songid) to
              <varname>TO</varname> (playlist index) in the
              playlist.  If <varname>TO</varname> is negative, it
              is relative to the current song in the playlist (if
              there is one).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlist">
          <term>
            <cmdsynopsis>
              <command>playlist</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Displays the current playlist.
            </para>
            <note>
              <para>
                Do not use this, instead use <link
                linkend="command_playlistinfo"><command>playlistinfo</command></link>.
              </para>
            </note>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlistfind">
          <term>
            <cmdsynopsis>
              <command>playlistfind</command>
              <arg choice="req"><replaceable>TAG</replaceable></arg>
              <arg choice="req"><replaceable>NEEDLE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Finds songs in the current playlist with strict
              matching.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlistid">
          <term>
            <cmdsynopsis>
              <command>playlistid</command>
              <arg choice="req"><replaceable>SONGID</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Displays a list of songs in the playlist.
              <varname>SONGID</varname> is optional and specifies a
              single song to display info for.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlistinfo">
          <term>
            <cmdsynopsis>
              <command>playlistinfo</command>
              <group>
                  <arg><replaceable>SONGPOS</replaceable></arg>
                  <arg><replaceable>START:END</replaceable></arg>
              </group>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Displays a list of all songs in the playlist, or if the optional
              argument is given, displays information only for the song
              <varname>SONGPOS</varname> or the range of songs
              <varname>START:END</varname>
              <footnoteref linkend="range_since_0_15"/>
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlistsearch">
          <term>
            <cmdsynopsis>
              <command>playlistsearch</command>
              <arg choice="req"><replaceable>TAG</replaceable></arg>
              <arg choice="req"><replaceable>NEEDLE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Searches case-insensitively for partial matches in the
              current playlist.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_plchanges">
          <term>
            <cmdsynopsis>
              <command>plchanges</command>
              <arg choice="req"><replaceable>VERSION</replaceable></arg>
              <arg><replaceable>START:END</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Displays changed songs currently in the playlist since
              <varname>VERSION</varname>.  Start and end positions may
              be given to limit the output to changes in the given
              range.
            </para>
            <para>
              To detect songs that were deleted at the end of the
              playlist, use playlistlength returned by status command.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_plchangesposid">
          <term>
            <cmdsynopsis>
              <command>plchangesposid</command>
              <arg choice="req"><replaceable>VERSION</replaceable></arg>
              <arg><replaceable>START:END</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Displays changed songs currently in the playlist since
              <varname>VERSION</varname>.  This function only
              returns the position and the id of the changed song, not
              the complete metadata. This is more bandwidth efficient.
            </para>
            <para>
              To detect songs that were deleted at the end of the
              playlist, use playlistlength returned by status command.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_prio">
          <term>
            <cmdsynopsis>
              <command>prio</command>
              <arg choice="req"><replaceable>PRIORITY</replaceable></arg>
              <arg choice="req" rep="repeat"><replaceable>START:END</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Set the priority of the specified songs.  A higher
              priority means that it will be played first when
              "random" mode is enabled.
            </para>

            <para>
              A priority is an integer between 0 and 255.  The default
              priority of new songs is 0.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_prioid">
          <term>
            <cmdsynopsis>
              <command>prioid</command>
              <arg choice="req"><replaceable>PRIORITY</replaceable></arg>
              <arg choice="req" rep="repeat"><replaceable>ID</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Same as <link
              linkend="command_prio"><command>prio</command></link>,
              but address the songs with their id.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_rangeid">
          <term>
            <cmdsynopsis>
              <command>rangeid</command>
              <arg choice="req"><replaceable>ID</replaceable></arg>
              <arg choice="req"><replaceable>START:END</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              <footnote id="since_0_19"><simpara>Since <application>MPD</application>
              0.19</simpara></footnote> Specifies the portion of the
              song that shall be played.  <varname>START</varname> and
              <varname>END</varname> are offsets in seconds
              (fractional seconds allowed); both are optional.
              Omitting both (i.e. sending just ":") means "remove the
              range, play everything".  A song that is currently
              playing cannot be manipulated this way.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_shuffle">
          <term>
            <cmdsynopsis>
              <command>shuffle</command>
              <arg><replaceable>START:END</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Shuffles the current playlist.
              <varname>START:END</varname> is optional and specifies
              a range of songs.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_swap">
          <term>
            <cmdsynopsis>
              <command>swap</command>
              <arg choice="req"><replaceable>SONG1</replaceable></arg>
              <arg choice="req"><replaceable>SONG2</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Swaps the positions of <varname>SONG1</varname> and
              <varname>SONG2</varname>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_swapid">
          <term>
            <cmdsynopsis>
              <command>swapid</command>
              <arg choice="req"><replaceable>SONG1</replaceable></arg>
              <arg choice="req"><replaceable>SONG2</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Swaps the positions of <varname>SONG1</varname> and
              <varname>SONG2</varname> (both song ids).
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_addtagid">
          <term>
            <cmdsynopsis>
              <command>addtagid</command>
              <arg choice="req"><replaceable>SONGID</replaceable></arg>
              <arg choice="req"><replaceable>TAG</replaceable></arg>
              <arg choice="req"><replaceable>VALUE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Adds a tag to the specified song.  Editing song tags is
              only possible for remote songs.  This change is
              volatile: it may be overwritten by tags received from
              the server, and the data is gone when the song gets
              removed from the queue.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_cleartagid">
          <term>
            <cmdsynopsis>
              <command>cleartagid</command>
              <arg choice="req"><replaceable>SONGID</replaceable></arg>
              <arg choice="opt"><replaceable>TAG</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Removes tags from the specified song.  If
              <varname>TAG</varname> is not specified, then all tag
              values will be removed.  Editing song tags is only
              possible for remote songs.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="playlist_files">
      <title>Stored playlists</title>

      <para>
        Playlists are stored inside the configured playlist directory.
        They are addressed with their file name (without the directory
        and without the <filename>.m3u</filename> suffix).
      </para>

      <para>
        Some of the commands described in this section can be used to
        run playlist plugins instead of the hard-coded simple
        <filename>m3u</filename> parser.  They can access playlists in
        the music directory (relative path including the suffix) or
        remote playlists (absolute URI with a supported scheme).
      </para>

      <variablelist>
        <varlistentry id="command_listplaylist">
          <term>
            <cmdsynopsis>
              <command>listplaylist</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Lists the songs in the playlist.  Playlist plugins are
              supported.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_listplaylistinfo">
          <term>
            <cmdsynopsis>
              <command>listplaylistinfo</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Lists the songs with metadata in the playlist.  Playlist
              plugins are supported.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_listplaylists">
          <term>
            <cmdsynopsis>
              <command>listplaylists</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Prints a list of the playlist directory.
            </para>
            <para>
              After each playlist name the server sends its last
              modification time as attribute "Last-Modified" in ISO
              8601 format.  To avoid problems due to clock differences
              between clients and the server, clients should not
              compare this value with their local clock.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_load">
          <term>
            <cmdsynopsis>
              <command>load</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="opt"><replaceable>START:END</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Loads the playlist into the current queue.  Playlist
              plugins are supported.  A range may be specified to load
              only a part of the playlist.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlistadd">
          <term>
            <cmdsynopsis>
              <command>playlistadd</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="req"><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Adds <varname>URI</varname> to the playlist
              <filename>NAME.m3u</filename>.
            </para>
            <para>
             <filename>NAME.m3u</filename> will be created if it does
             not exist.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlistclear">
          <term>
            <cmdsynopsis>
              <command>playlistclear</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Clears the playlist <filename>NAME.m3u</filename>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlistdelete">
          <term>
            <cmdsynopsis>
              <command>playlistdelete</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="req"><replaceable>SONGPOS</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Deletes <varname>SONGPOS</varname> from the
              playlist <filename>NAME.m3u</filename>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_playlistmove">
          <term>
            <cmdsynopsis>
              <command>playlistmove</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="req"><replaceable>FROM</replaceable></arg>
              <arg choice="req"><replaceable>TO</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Moves the song at position <varname>FROM</varname> in
              the playlist <filename>NAME.m3u</filename> to the
              position <varname>TO</varname>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_rename">
          <term>
            <cmdsynopsis>
              <command>rename</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="req"><replaceable>NEW_NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Renames the playlist <filename>NAME.m3u</filename> to <filename>NEW_NAME.m3u</filename>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_rm">
          <term>
            <cmdsynopsis>
              <command>rm</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Removes the playlist <filename>NAME.m3u</filename> from
              the playlist directory.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_save">
          <term>
            <cmdsynopsis>
              <command>save</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Saves the current playlist to
              <filename>NAME.m3u</filename> in the playlist directory.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="database">
      <title>The music database</title>

      <variablelist>
        <varlistentry id="album_art">
          <term>
            <cmdsynopsis>
              <command>albumart</command>
              <arg choice="req"><replaceable>URI</replaceable></arg>
              <arg choice="req"><replaceable>OFFSET</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Searches the directory the file <varname>URI</varname>
              resides in and attempts to return a chunk of an album
              art image file at offset <varname>OFFSET</varname>.
            </para>
            <para>
              Uses the filename "cover" with any of ".png, .jpg,
              .tiff, .bmp".
            </para>
            <para>
              Returns the file size and actual number
              of bytes read at the requested offset, followed
              by the chunk requested as raw bytes, then a
              newline and the completion code.
            </para>
            <para>
              Example:
            </para>

            <programlisting>albumart
size: 1024768
binary: 8192
&lt;8192 bytes&gt;
OK
</programlisting>
          </listitem>
        </varlistentry>

        <varlistentry id="command_count">
          <term>
            <cmdsynopsis>
              <command>count</command>
              <arg choice="req" rep="repeat"><replaceable>FILTER</replaceable></arg>
              <arg choice="opt">group</arg>
              <arg choice="opt"><replaceable>GROUPTYPE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Count the number of songs and their total playtime in
              the database matching <varname>FILTER</varname> (see
              <link linkend="filter_syntax">Filters</link>).  The
              following prints the number of songs whose title matches
              "Echoes":
            </para>
            <programlisting>count title Echoes</programlisting>
            <para>
              The <parameter>group</parameter> keyword may be used to
              group the results by a tag.  The first following example
              prints per-artist counts while the next prints the
              number of songs whose title matches "Echoes" grouped by
              artist:
            </para>
            <programlisting>count group artist</programlisting>
            <programlisting>count title Echoes group artist</programlisting>
          </listitem>
        </varlistentry>

        <varlistentry id="command_find">
          <term>
            <cmdsynopsis>
              <command>find</command>
              <arg choice="req" rep="repeat"><replaceable>FILTER</replaceable></arg>
              <arg choice="opt">sort <replaceable>TYPE</replaceable></arg>
              <arg choice="opt">window <replaceable>START</replaceable>:<replaceable>END</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Search the database for songs matching
              <varname>FILTER</varname> (see <link
              linkend="filter_syntax">Filters</link>).
            </para>

            <para>
              <varname>sort</varname> sorts the result by the
              specified tag.  The sort is descending if the tag is
              prefixed with a minus ('-').
              Without <varname>sort</varname>, the
              order is undefined.  Only the first tag value will be
              used, if multiple of the same type exist.  To sort by
              "Artist", "Album" or "AlbumArtist", you should specify
              "ArtistSort", "AlbumSort" or "AlbumArtistSort" instead.
              These will automatically fall back to the former if
              "*Sort" doesn't exist.  "AlbumArtist" falls back to just
              "Artist".  The type "Last-Modified" can sort by file
              modification time.
            </para>

            <para>
              <varname>window</varname> can be used to query only a
              portion of the real response.  The parameter is two
              zero-based record numbers; a start number and an end
              number.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_findadd">
          <term>
            <cmdsynopsis>
              <command>findadd</command>
              <arg choice="req" rep="repeat"><replaceable>FILTER</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Search the database for songs matching
              <varname>FILTER</varname> (see <link
              linkend="filter_syntax">Filters</link>) and add them to
              the queue.  Parameters have the same meaning as for
              <link
              linkend="command_find"><command>find</command></link>.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_list">
          <term>
            <cmdsynopsis>
              <command>list</command>
              <arg choice="req"><replaceable>TYPE</replaceable></arg>
              <arg choice="opt" rep="repeat"><replaceable>FILTER</replaceable></arg>
              <arg choice="opt" rep="repeat">
                <arg choice="req">group</arg>
                <arg choice="req"><replaceable>GROUPTYPE</replaceable></arg>
              </arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Lists unique tags values of the specified type.
              <varname>TYPE</varname> can be any tag supported by
              <application>MPD</application> or
              <parameter>file</parameter>.
            </para>
            <para>
              Additional arguments may specify a <link
              linkend="filter_syntax">filter</link>.
            </para>
            <para>
              The <parameter>group</parameter> keyword may be used
              (repeatedly) to group the results by one or more tags.
              The following example lists all album names,
              grouped by their respective (album) artist:
            </para>
            <programlisting>list album group albumartist</programlisting>
          </listitem>
        </varlistentry>

        <varlistentry id="command_listall">
          <term>
            <cmdsynopsis>
              <command>listall</command>
              <arg><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Lists all songs and directories in
              <varname>URI</varname>.
            </para>
            <para>
              Do not use this command.  Do not manage a client-side
              copy of <application>MPD</application>'s database.  That
              is fragile and adds huge overhead.  It will break with
              large databases.  Instead, query
              <application>MPD</application> whenever you need
              something.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_listallinfo">
          <term>
            <cmdsynopsis>
              <command>listallinfo</command>
              <arg><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Same as <link
              linkend="command_listall"><command>listall</command></link>,
              except it also returns metadata info in the same format
              as <link
              linkend="command_lsinfo"><command>lsinfo</command></link>
            </para>
            <para>
              Do not use this command.  Do not manage a client-side
              copy of <application>MPD</application>'s database.  That
              is fragile and adds huge overhead.  It will break with
              large databases.  Instead, query
              <application>MPD</application> whenever you need
              something.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_listfiles">
          <term>
            <cmdsynopsis>
              <command>listfiles</command>
              <arg><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Lists the contents of the directory
              <varname>URI</varname>, including files are not
              recognized by <application>MPD</application>.
              <varname>URI</varname> can be a path relative to the
              music directory or an URI understood by one of the
              storage plugins.  The response contains at least one
              line for each directory entry with the prefix "file: "
              or "directory: ", and may be followed by file attributes
              such as "Last-Modified" and "size".
            </para>
            <para>
              For example, "smb://SERVER" returns a list of all shares
              on the given SMB/CIFS server; "nfs://servername/path"
              obtains a directory listing from the NFS server.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_lsinfo">
          <term>
            <cmdsynopsis>
              <command>lsinfo</command>
              <arg><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Lists the contents of the directory
              <varname>URI</varname>.  The response contains records
              starting with <varname>file</varname>,
              <varname>directory</varname> or
              <varname>playlist</varname>, each followed by metadata
              (<link linkend="tags">tags</link> or <link
              linkend="other_metadata">other metadata</link>).
            </para>
            <para>
              When listing the root directory, this currently returns
              the list of stored playlists.  This behavior is
              deprecated; use "listplaylists" instead.
            </para>
            <para>
              This command may be used to list metadata of remote
              files (e.g. URI beginning with "http://" or "smb://").
            </para>
            <para>
              Clients that are connected via UNIX domain socket may
              use this command to read the tags of an arbitrary local
              file (URI is an absolute path).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_readcomments">
          <term>
            <cmdsynopsis>
              <command>readcomments</command>
              <arg><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Read "comments" (i.e. key-value pairs) from the file
              specified by "URI".  This "URI" can be a path relative
              to the music directory or an absolute path.
            </para>
            <para>
              This command may be used to list metadata of remote
              files (e.g. URI beginning with "http://" or "smb://").
            </para>
            <para>
              The response consists of lines in the form "KEY: VALUE".
              Comments with suspicious characters (e.g. newlines) are
              ignored silently.
            </para>
            <para>
              The meaning of these depends on the codec, and not all
              decoder plugins support it.  For example, on Ogg files,
              this lists the Vorbis comments.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_search">
          <term>
            <cmdsynopsis>
              <command>search</command>
              <arg choice="req" rep="repeat"><replaceable>FILTER</replaceable></arg>
              <arg choice="opt">sort <replaceable>TYPE</replaceable></arg>
              <arg choice="opt">window <replaceable>START</replaceable>:<replaceable>END</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Search the database for songs matching
              <varname>FILTER</varname> (see <link
              linkend="filter_syntax">Filters</link>).  Parameters
              have the same meaning as for <link
              linkend="command_find"><command>find</command></link>,
              except that search is not case sensitive.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_searchadd">
          <term>
            <cmdsynopsis>
              <command>searchadd</command>
              <arg choice="req" rep="repeat"><replaceable>FILTER</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Search the database for songs matching
              <varname>FILTER</varname> (see <link
              linkend="filter_syntax">Filters</link>) and add them to
              the queue.
            </para>
            <para>
              Parameters have the same meaning as for <link
              linkend="command_search"><command>search</command></link>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_searchaddpl">
          <term>
            <cmdsynopsis>
              <command>searchaddpl</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="req" rep="repeat"><replaceable>FILTER</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Search the database for songs matching
              <varname>FILTER</varname> (see <link
              linkend="filter_syntax">Filters</link>) and add them to
              the playlist named <varname>NAME</varname>.
            </para>
            <para>
              If a playlist by that name doesn't exist it is created.
            </para>
            <para>
              Parameters have the same meaning as for <link
              linkend="command_search"><command>search</command></link>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_update">
          <term>
            <cmdsynopsis>
              <command>update</command>
              <arg choice="opt"><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Updates the music database: find new files, remove
              deleted files, update modified files.
            </para>
            <para>
              <varname>URI</varname> is a particular directory or
              song/file to update.  If you do not specify it,
              everything is updated.
            </para>
            <para>
              Prints "updating_db: JOBID" where
              <varname>JOBID</varname> is a positive number
              identifying the update job.  You can read the current
              job id in the <link
              linkend="command_status"><command>status</command></link>
              response.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_rescan">
          <term>
            <cmdsynopsis>
              <command>rescan</command>
              <arg choice="opt"><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Same as <link
              linkend="command_update"><command>update</command></link>,
              but also rescans unmodified files.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="mount">
      <title>Mounts and neighbors</title>

      <para>
        A "storage" provides access to files in a directory tree.  The
        most basic storage plugin is the "local" storage plugin which
        accesses the local file system, and there are plugins to
        access NFS and SMB servers.
      </para>

      <para>
        Multiple storages can be "mounted" together, similar to the
        <application>mount</application> command on many operating
        systems, but without cooperation from the kernel.  No
        superuser privileges are necessary, beause this mapping exists
        only inside the <application>MPD</application> process
      </para>

      <variablelist>

        <varlistentry id="command_mount">
          <term>
            <cmdsynopsis>
              <command>mount</command>
              <arg choice="req"><replaceable>PATH</replaceable></arg>
              <arg choice="req"><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>

          <listitem>
            <para>
              Mount the specified remote storage URI at the given
              path.  Example:
            </para>

            <programlisting>mount foo nfs://192.168.1.4/export/mp3</programlisting>
          </listitem>
        </varlistentry>

        <varlistentry id="command_umount">
          <term>
            <cmdsynopsis>
              <command>unmount</command>
              <arg choice="req"><replaceable>PATH</replaceable></arg>
            </cmdsynopsis>
          </term>

          <listitem>
            <para>
              Unmounts the specified path.  Example:
            </para>

            <programlisting>unmount foo</programlisting>
          </listitem>
        </varlistentry>

        <varlistentry id="command_listmounts">
          <term>
            <cmdsynopsis>
              <command>listmounts</command>
            </cmdsynopsis>
          </term>

          <listitem>
            <para>
              Queries a list of all mounts.  By default, this contains
              just the configured <varname>music_directory</varname>.
              Example:
            </para>

            <programlisting>listmounts
mount: 
storage: /home/foo/music
mount: foo
storage: nfs://192.168.1.4/export/mp3
OK
</programlisting>
          </listitem>
        </varlistentry>

        <varlistentry id="command_listneighbors">
          <term>
            <cmdsynopsis>
              <command>listneighbors</command>
            </cmdsynopsis>
          </term>

          <listitem>
            <para>
              Queries a list of "neighbors" (e.g. accessible file
              servers on the local net).  Items on that list may be
              used with the <link
              linkend="command_mount"><command>mount</command></link>
              command.  Example:
            </para>

            <programlisting>listneighbors
neighbor: smb://FOO
name: FOO (Samba 4.1.11-Debian)
OK
</programlisting>
          </listitem>
        </varlistentry>

      </variablelist>
    </section>

    <section id="stickers">
      <title>Stickers</title>

      <para>
        "Stickers"<footnoteref linkend="since_0_15"/> are pieces of
        information attached to existing
        <application>MPD</application> objects (e.g. song files,
        directories, albums).  Clients can create arbitrary name/value
        pairs.  <application>MPD</application> itself does not assume
        any special meaning in them.
      </para>

      <para>
        The goal is to allow clients to share additional (possibly
        dynamic) information about songs, which is neither stored on
        the client (not available to other clients), nor stored in the
        song files (<application>MPD</application> has no write
        access).
      </para>

      <para>
        Client developers should create a standard for common sticker
        names, to ensure interoperability.
      </para>

      <para>
        Objects which may have stickers are addressed by their object
        type ("song" for song objects) and their URI (the path within
        the database for songs).
      </para>

      <variablelist>
        <varlistentry id="command_sticker_get">
          <term>
            <cmdsynopsis>
              <command>sticker</command>
              <arg choice="plain">get</arg>
              <arg choice="req"><replaceable>TYPE</replaceable></arg>
              <arg choice="req"><replaceable>URI</replaceable></arg>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Reads a sticker value for the specified object.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_sticker_set">
          <term>
            <cmdsynopsis>
              <command>sticker</command>
              <arg choice="plain">set</arg>
              <arg choice="req"><replaceable>TYPE</replaceable></arg>
              <arg choice="req"><replaceable>URI</replaceable></arg>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="req"><replaceable>VALUE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Adds a sticker value to the specified object.  If a
              sticker item with that name already exists, it is
              replaced.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_sticker_delete">
          <term>
            <cmdsynopsis>
              <command>sticker</command>
              <arg choice="plain">delete</arg>
              <arg choice="req"><replaceable>TYPE</replaceable></arg>
              <arg choice="req"><replaceable>URI</replaceable></arg>
              <arg choice="opt"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Deletes a sticker value from the specified object.  If
              you do not specify a sticker name, all sticker values
              are deleted.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_sticker_list">
          <term>
            <cmdsynopsis>
              <command>sticker</command>
              <arg choice="plain">list</arg>
              <arg choice="req"><replaceable>TYPE</replaceable></arg>
              <arg choice="req"><replaceable>URI</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Lists the stickers for the specified object.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_sticker_find">
          <term>
            <cmdsynopsis>
              <command>sticker</command>
              <arg choice="plain">find</arg>
              <arg choice="req"><replaceable>TYPE</replaceable></arg>
              <arg choice="req"><replaceable>URI</replaceable></arg>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Searches the sticker database for stickers with the
              specified name, below the specified directory (URI).
              For each matching song, it prints the URI and that one
              sticker's value.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_sticker_find_equals">
          <term>
            <cmdsynopsis>
              <command>sticker</command>
              <arg choice="plain">find</arg>
              <arg choice="req"><replaceable>TYPE</replaceable></arg>
              <arg choice="req"><replaceable>URI</replaceable></arg>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="plain">=</arg>
              <arg choice="req"><replaceable>VALUE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Searches for stickers with the given value.
            </para>

            <para>
              Other supported operators are:
              "<function>&lt;</function>", "<function>&gt;</function>"
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="connection_commands">
      <title>Connection settings</title>

      <variablelist>
        <varlistentry id="command_close">
          <term>
            <cmdsynopsis>
              <command>close</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Closes the connection to <application>MPD</application>.
              <application>MPD</application> will try to send the
              remaining output buffer before it actually closes the
              connection, but that cannot be guaranteed.  This command
              will not generate a response.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_kill">
          <term>
            <cmdsynopsis>
              <command>kill</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Kills <application>MPD</application>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_password">
          <term>
            <cmdsynopsis>
              <command>password</command>
              <arg choice="req"><replaceable>PASSWORD</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              This is used for authentication with the server.
              <varname>PASSWORD</varname> is simply the plaintext
              password.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_ping">
          <term>
            <cmdsynopsis>
              <command>ping</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Does nothing but return "OK".
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_tagtypes">
          <term>
            <cmdsynopsis>
              <command>tagtypes</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Shows a list of available tag types.  It is an
              intersection of the <varname>metadata_to_use</varname>
              setting and this client's tag mask.
            </para>

            <para>
              About the tag mask: each client can decide to disable
              any number of tag types, which will be omitted from
              responses to this client.  That is a good idea, because
              it makes responses smaller.  The following
              <command>tagtypes</command> sub commands configure this
              list.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_tagtypes_disable">
          <term>
            <cmdsynopsis>
              <command>tagtypes</command>
              <arg choice="plain">disable</arg>
              <arg choice="req" rep="repeat"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Remove one or more tags from the list of tag types the
              client is interested in.  These will be omitted from
              responses to this client.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_tagtypes_enable">
          <term>
            <cmdsynopsis>
              <command>tagtypes</command>
              <arg choice="plain">enable</arg>
              <arg choice="req" rep="repeat"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Re-enable one or more tags from the list of tag types
              for this client.  These will no longer be hidden from
              responses to this client.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_tagtypes_clear">
          <term>
            <cmdsynopsis>
              <command>tagtypes</command>
              <arg choice="plain">clear</arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Clear the list of tag types this client is interested
              in.  This means that <application>MPD</application> will
              not send any tags to this client.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_tagtypes_all">
          <term>
            <cmdsynopsis>
              <command>tagtypes</command>
              <arg choice="plain">all</arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Announce that this client is interested in all tag
              types.  This is the default setting for new clients.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="partition_commands">
      <title>Partition commands</title>

      <para>
        These commands allow a client to inspect and manage
        "partitions".  A partition is one frontend of a multi-player
        MPD process: it has separate queue, player and outputs.  A
        client is assigned to one partition at a time.
      </para>

      <variablelist>
        <varlistentry id="command_partition">
          <term>
            <cmdsynopsis>
              <command>partition</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Switch the client to a different partition.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_listpartitions">
          <term>
            <cmdsynopsis>
              <command>listpartitions</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Print a list of partitions.  Each partition starts with
              a <varname>partition</varname> keyword and the
              partition's name, followed by information about the
              partition.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_newpartition">
          <term>
            <cmdsynopsis>
              <command>newpartition</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Create a new partition.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="output_commands">
      <title>Audio output devices</title>

      <variablelist>
        <varlistentry id="command_disableoutput">
          <term>
            <cmdsynopsis>
              <command>disableoutput</command>
              <arg choice="req"><replaceable>ID</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Turns an output off.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_enableoutput">
          <term>
            <cmdsynopsis>
              <command>enableoutput</command>
              <arg choice="req"><replaceable>ID</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Turns an output on.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_toggleoutput">
          <term>
            <cmdsynopsis>
              <command>toggleoutput</command>
              <arg choice="req"><replaceable>ID</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Turns an output on or off, depending on the current
              state.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_outputs">
          <term>
            <cmdsynopsis>
              <command>outputs</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Shows information about all outputs.
            </para>
            <screen>
outputid: 0
outputname: My ALSA Device
plugin: alsa
outputenabled: 0
attribute: dop=0
OK
            </screen>
            <para>
              Return information:
            </para>
            <itemizedlist>
              <listitem>
                <para>
                  <varname>outputid</varname>: ID of the output. May change between executions
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>outputname</varname>: Name of the output. It can be any.
                </para>
              </listitem>
              <listitem>
                <para>
                  <varname>outputenabled</varname>: Status of the output. 0 if disabled, 1 if enabled.
                </para>
              </listitem>
            </itemizedlist>
          </listitem>
        </varlistentry>

        <varlistentry id="command_outputset">
          <term>
            <cmdsynopsis>
              <command>outputset</command>
              <arg choice="req"><replaceable>ID</replaceable></arg>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
              <arg choice="req"><replaceable>VALUE</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Set a runtime attribute.  These are specific to the
              output plugin, and supported values are usually printed
              in the <link
              linkend="command_outputs"><command>outputs</command></link>
              response.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="reflection_commands">
      <title>Reflection</title>

      <variablelist>
        <varlistentry id="command_config">
          <term>
            <cmdsynopsis>
              <command>config</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Dumps configuration values that may be interesting for
              the client.  This command is only permitted to "local"
              clients (connected via UNIX domain socket).
            </para>
            <para>
              The following response attributes are available:
            </para>
            <informaltable>
              <tgroup cols="2">
                <thead>
                  <row>
                    <entry>
                      Name
                    </entry>
                    <entry>
                      Description
                    </entry>
                  </row>
                </thead>
                <tbody>
                  <row>
                    <entry>
                      <varname>music_directory</varname>
                    </entry>
                    <entry>
                      The absolute path of the music directory.
                    </entry>
                  </row>
                </tbody>
              </tgroup>
            </informaltable>
          </listitem>
        </varlistentry>
        <varlistentry id="command_commands">
          <term>
            <cmdsynopsis>
              <command>commands</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Shows which commands the current user has access to.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_notcommands">
          <term>
            <cmdsynopsis>
              <command>notcommands</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Shows which commands the current user does not have
              access to.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_urlhandlers">
          <term>
            <cmdsynopsis>
              <command>urlhandlers</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Gets a list of available URL handlers.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry id="command_decoders">
          <term>
            <cmdsynopsis>
              <command>decoders</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Print a list of decoder plugins, followed by their
              supported suffixes and MIME types.  Example response:
            </para>
            <programlisting>plugin: mad
suffix: mp3
suffix: mp2
mime_type: audio/mpeg
plugin: mpcdec
suffix: mpc</programlisting>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>

    <section id="client_to_client">
      <title>Client to client</title>

      <para>
        Clients can communicate with each others over "channels".  A
        channel is created by a client subscribing to it.  More than
        one client can be subscribed to a channel at a time; all of
        them will receive the messages which get sent to it.
      </para>

      <para>
        Each time a client subscribes or unsubscribes, the global idle
        event <varname>subscription</varname> is generated.  In
        conjunction with the <link
        linkend="command_channels"><command>channels</command></link>
        command, this may be used to auto-detect clients providing
        additional services.
      </para>

      <para>
        New messages are indicated by the <varname>message</varname>
        idle event.
      </para>

      <variablelist>
        <varlistentry id="command_subscribe">
          <term>
            <cmdsynopsis>
              <command>subscribe</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Subscribe to a channel.  The channel is created if it
              does not exist already.  The name may consist of
              alphanumeric ASCII characters plus underscore, dash, dot
              and colon.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_unsubscribe">
          <term>
            <cmdsynopsis>
              <command>unsubscribe</command>
              <arg choice="req"><replaceable>NAME</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Unsubscribe from a channel.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_channels">
          <term>
            <cmdsynopsis>
              <command>channels</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Obtain a list of all channels.  The response is a list
              of "channel:" lines.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_readmessages">
          <term>
            <cmdsynopsis>
              <command>readmessages</command>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Reads messages for this client.  The response is a list
              of "channel:" and "message:" lines.
            </para>
          </listitem>
        </varlistentry>

        <varlistentry id="command_sendmessage">
          <term>
            <cmdsynopsis>
              <command>sendmessage</command>
              <arg choice="req"><replaceable>CHANNEL</replaceable></arg>
              <arg choice="req"><replaceable>TEXT</replaceable></arg>
            </cmdsynopsis>
          </term>
          <listitem>
            <para>
              Send a message to the specified channel.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
  </chapter>
</book>