<?xml version='1.0' encoding='UTF-8'?>
<?xml-stylesheet type="text/xsl" href="manpage.xsl"?>

<refentry xml:id="mosquitto_sub" xmlns:xlink="http://www.w3.org/1999/xlink">
	<refmeta>
		<refentrytitle>mosquitto_sub</refentrytitle>
		<manvolnum>1</manvolnum>
		<refmiscinfo class="source">Mosquitto Project</refmiscinfo>
		<refmiscinfo class="manual">Commands</refmiscinfo>
	</refmeta>

	<refnamediv>
		<refname>mosquitto_sub</refname>
		<refpurpose>an MQTT version 5/3.1.1/3.1 client for subscribing to topics</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
		<cmdsynopsis>
			<command>mosquitto_sub</command>
			<group choice='req'>
				<arg choice='plain'>
					<arg><option>-h</option> <replaceable>hostname</replaceable></arg>
					<arg><option>-p</option> <replaceable>port-number</replaceable></arg>
					<arg><option>-u</option> <replaceable>username</replaceable></arg>
					<arg><option>-P</option> <replaceable>password</replaceable></arg>
					<arg choice='plain' rep='repeat'><option>-t</option> <replaceable>message-topic</replaceable></arg>
				</arg>
				<arg choice='plain'>
					<arg choice='plain'><option>-L</option> <replaceable>URL</replaceable></arg>
					<arg choice='opt' rep='repeat'><option>-t</option> <replaceable>message-topic</replaceable></arg>
				</arg>
			</group>
			<arg><option>-A</option> <replaceable>bind-address</replaceable></arg>
			<arg><option>-c</option></arg>
			<arg><option>-C</option> <replaceable>msg-count</replaceable></arg>
			<arg><option>-d</option></arg>
			<arg><option>-D</option> <replaceable>command</replaceable> <replaceable>identifier</replaceable> <replaceable>value</replaceable></arg>
			<arg><option>-E</option></arg>
			<arg><option>-i</option> <replaceable>client-id</replaceable></arg>
			<arg><option>-I</option> <replaceable>client-id-prefix</replaceable></arg>
			<arg><option>-k</option> <replaceable>keepalive-time</replaceable></arg>
			<arg><option>-N</option></arg>
			<arg><option>-q</option> <replaceable>message-QoS</replaceable></arg>
			<arg><option>--remove-retained</option></arg>
			<group choice='opt'>
				<arg choice='plain'><option>-R</option></arg>
				<arg choice='plain'><option>--retained-only</option></arg>
			</group>
			<arg><option>--retain-as-published</option></arg>
			<arg><option>-S</option></arg>
			<arg choice='opt' rep='repeat'><option>-T</option> <replaceable>filter-out</replaceable></arg>
			<arg choice='opt' rep='repeat'><option>-U</option> <replaceable>unsub-topic</replaceable></arg>
			<arg><option>-v</option></arg>
			<arg><option>-V</option> <replaceable>protocol-version</replaceable></arg>
			<arg><option>-W</option> <replaceable>message-processing-timeout</replaceable></arg>
			<arg><option>--proxy</option> <replaceable>socks-url</replaceable></arg>
			<arg><option>--quiet</option></arg>
			<arg>
				<option>--will-topic</option> <replaceable>topic</replaceable>
				<arg><option>--will-payload</option> <replaceable>payload</replaceable></arg>
				<arg><option>--will-qos</option> <replaceable>qos</replaceable></arg>
				<arg><option>--will-retain</option></arg>
			</arg>
			<group>
				<arg>
					<group choice='req'>
						<arg choice='plain'><option>--cafile</option> <replaceable>file</replaceable></arg>
						<arg choice='plain'><option>--capath</option> <replaceable>dir</replaceable></arg>
					</group>
					<arg><option>--cert</option> <replaceable>file</replaceable></arg>
					<arg><option>--key</option> <replaceable>file</replaceable></arg>
					<arg><option>--tls-version</option> <replaceable>version</replaceable></arg>
					<arg><option>--tls-alpn</option> <replaceable>protocol</replaceable></arg>
					<arg><option>--tls-engine</option> <replaceable>engine</replaceable></arg>
					<arg><option>--keyform</option>
					<group choice='req'>
						<arg choice='plain'><replaceable>pem</replaceable></arg>
						<arg choice='plain'><replaceable>engine</replaceable></arg>
					</group></arg>
					<arg><option>--tls-engine-kpass-sha1</option> <replaceable>kpass-sha1</replaceable></arg>
					<arg><option>--insecure</option></arg>
				</arg>
				<arg>
					<arg choice='plain'><option>--psk</option> <replaceable>hex-key</replaceable></arg>
					<arg choice='plain'><option>--psk-identity</option> <replaceable>identity</replaceable></arg>
					<arg><option>--tls-version</option> <replaceable>version</replaceable></arg>
				</arg>
			</group>
		</cmdsynopsis>
		<cmdsynopsis>
			<command>mosquitto_sub</command>
			<group choice='plain'>
				<arg><option>--help</option></arg>
			</group>
		</cmdsynopsis>
	</refsynopsisdiv>

	<refsect1>
		<title>Description</title>
		<para><command>mosquitto_sub</command> is a simple MQTT version 5/3.1.1
			client that will subscribe to topics and print the messages that
			it receives.</para>
		<para>In addition to subscribing to topics,
			<command>mosquitto_sub</command> can filter out received messages
			so they are not printed (see the <option>-T</option> option) or
			unsubscribe from topics (see the <option>-U</option> option).
			Unsubscribing from topics is useful for clients connecting with
			clean session set to false. </para>
	</refsect1>

	<refsect1>
		<title>Encrypted Connections</title>
		<para><command>mosquitto_sub</command> supports TLS encrypted
			connections. It is strongly recommended that you use an encrypted
			connection for anything more than the most basic setup.</para>
		<para>To enable TLS connections when using x509 certificates, one of
			either <option>--cafile</option> or <option>--capath</option> must
			be provided as an option.</para>
		<para>To enable TLS connections when using TLS-PSK, you must use the
			<option>--psk</option> and the <option>--psk-identity</option>
			options.</para>
	</refsect1>

	<refsect1>
		<title>Options</title>
		<para>The options below may be given on the command line, but may also
			be placed in a config file located at
			<option>$XDG_CONFIG_HOME/mosquitto_sub</option> or
			<option>$HOME/.config/mosquitto_sub</option> with one pair of
			<option>-option <replaceable>value</replaceable></option>
			per line. The values in the config file will be used as defaults
			and can be overridden by using the command line. The exceptions to
			this are <option>-t</option> and <option>-T</option>, which if
			given in the config file will not be overridden. Note also that
			currently some options cannot be negated, e.g.
			<option>-S</option>. Config file lines that have a
			<option>#</option> as the first character are treated as comments
			and not processed any further.</para>
		<variablelist>
			<varlistentry>
				<term><option>-A</option></term>
				<listitem>
					<para>Bind the outgoing connection to a local ip
						address/hostname. Use this argument if you need to
						restrict network communication to a particular
						interface.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-c</option></term>
				<term><option>--disable-clean-session</option></term>
				<listitem>
					<para>Disable the 'clean session' flag. This means that all
					of the subscriptions for the client will be maintained
					after it disconnects, along with subsequent QoS 1 and QoS 2
					messages that arrive. When the client reconnects, it will
					receive all of the queued messages.</para>
					<para>If using this option, the client id must be set
						manually with <option>--id</option></para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--cafile</option></term>
				<listitem>
					<para>Define the path to a file containing PEM encoded CA
						certificates that are trusted. Used to enable SSL
						communication.</para>
					<para>See also <option>--capath</option></para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--capath</option></term>
				<listitem>
					<para>Define the path to a directory containing PEM encoded CA
						certificates that are trusted. Used to enable SSL
						communication.</para>
					<para>For <option>--capath</option> to work correctly, the
						certificate files must have ".crt" as the file ending
						and you must run "openssl rehash &lt;path to capath&gt;" each
						time you add/remove a certificate.</para>
					<para>See also <option>--cafile</option></para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--cert</option></term>
				<listitem>
					<para>Define the path to a file containing a PEM encoded
						certificate for this client, if required by the
						server.</para>
					<para>See also <option>--key</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--ciphers</option></term>
				<listitem>
					<para>An openssl compatible list of TLS ciphers to support
						in the client. See
						<citerefentry><refentrytitle>ciphers</refentrytitle><manvolnum>1</manvolnum></citerefentry>
						for more information.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-C</option></term>
				<listitem>
					<para>Disconnect and exit the program immediately after
						the given count of messages have been received. This
						may be useful in shell scripts where on a single status
						value is required, for example.</para>
					<para>Combine with <option>-R</option> to print only the
						first set of fresh messages (i.e. that does not have
						the retained flag set), or with <option>-T</option> to
						filter which topics are processed.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-d</option></term>
				<term><option>--debug</option></term>
				<listitem>
					<para>Enable debug messages.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-D</option></term>
				<term><option>--property</option></term>
				<listitem>
					<para>Use an MQTT v5 property with this publish. If you use
						this option, the client will be set to be an MQTT v5
						client. This option has two forms:</para>
					<para><option>-D command identifier value</option></para>
					<para><option>-D command identifier name value</option></para>
					<para><option>command</option> is the MQTT command/packet
						identifier and can be one of CONNECT, PUBACK, PUBREC,
						PUBCOMP, SUBSCRIBE, UNSUBSCRIBE, DISCONNECT, AUTH, or
						WILL. The properties available for each command are
						listed in the Properties section.</para>

					<para><option>identifier</option> is the name of the
						property to add. This is as described in the
						specification, but with '-' as a word separator. For
						example:
						<option>payload-format-indicator</option>. More details
						are in the <link linkend='properties'>Properties</link>
						section.</para>

					<para><option>value</option> is the value of the property
						to add, with a data type that is property
						specific.</para>

					<para><option>name</option> is only used for the
						<option>user-property</option> property as the first of
						the two strings in the string pair. In that case,
						<option>value</option> is the second of the strings in
						the pair.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-E</option></term>
				<listitem>
					<para>If this option is given,
						<command>mosquitto_sub</command> will exit immediately
						that all of its subscriptions have been acknowledged by
						the broker. In conjunction with <option>-c</option>
						this allows a durable client session to be initialised
						on the broker for future use without requiring any
						messages to be received.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-F</option></term>
				<listitem>
					<para>Specify output printing format. This option allows
						you to choose what information from each message is
						printed to the screen. See the <link
							linkend='outputformat'>Output Format</link> section
						below for full details.</para>
					<para>This option overrides the <option>-v</option> option,
						but does not override the <option>-N</option>
						option.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--help</option></term>
				<listitem>
					<para>Display usage information.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-h</option></term>
				<term><option>--host</option></term>
				<listitem>
					<para>Specify the host to connect to. Defaults to localhost.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-i</option></term>
				<term><option>--id</option></term>
				<listitem>
					<para>The id to use for this client. If not given, a client id will
					be generated depending on the MQTT version being used. For v3.1.1/v3.1,
					the client generates a client id in the format
					<option>mosq-XXXXXXXXXXXXXXXXXX</option>, where the
					<option>X</option> are replaced with random alphanumeric
					characters. For v5.0, the client sends a zero length client id, and the
					server will generate a client id for the client.</para>

					<para>This option cannot be used at the same time as the
					<option>--id-prefix</option> argument.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-I</option></term>
				<term><option>--id-prefix</option></term>
				<listitem>
					<para>Provide a prefix that the client id will be built
					from by appending the process id of the client. This is
					useful where the broker is using the clientid_prefixes
					option. Cannot be used at the same time as the
					<option>--id</option> argument.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--insecure</option></term>
				<listitem>
					<para>When using certificate based encryption, this option
						disables verification of the server hostname in the
						server certificate. This can be useful when testing
						initial server configurations but makes it possible for
						a malicious third party to impersonate your server
						through DNS spoofing, for example. Use this option in
						testing <emphasis>only</emphasis>. If you need to
						resort to using this option in a production
						environment, your setup is at fault and there is no
						point using encryption.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-k</option></term>
				<term><option>--keepalive</option></term>
				<listitem>
					<para>The number of seconds between sending PING commands
					to the broker for the purposes of informing it we are still
					connected and functioning. Defaults to 60 seconds.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--key</option></term>
				<listitem>
					<para>Define the path to a file containing a PEM encoded
						private key for this client, if required by the
						server.</para>
					<para>See also <option>--cert</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--keyform</option></term>
				<listitem>
					<para>Specifies the type of private key in use when making
						TLS connections.. This can be "pem" or "engine". This
						parameter is useful when a TPM module is being used and
						the private key has been created with it. Defaults to
						"pem", which means normal private key files are
						used.</para>
					<para>See also <option>--tls-engine</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-L</option></term>
				<term><option>--url</option></term>
				<listitem>
					<para>Specify specify user, password, hostname, port and
						topic at once as a URL.  The URL must be in the form:
						mqtt(s)://[username[:password]@]host[:port]/topic</para>
					<para>If the scheme is mqtt:// then the port defaults to
						1883. If the scheme is mqtts:// then the port defaults
						to 8883.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-N</option></term>
				<listitem>
					<para>Do not append an end of line character to the payload
						when printing. This allows streaming of payload data
						from multiple messages directly to another application
						unmodified. Only really makes sense when not using
						<option>-v</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-p</option></term>
				<term><option>--port</option></term>
				<listitem>
					<para>Connect to the port specified. If not given, the
						default of 1883 for plain MQTT or 8883 for MQTT over
						TLS will be used.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-P</option></term>
				<term><option>--pw</option></term>
				<listitem>
					<para>Provide a password to be used for authenticating with
						the broker. Using this argument without also specifying
						a username is invalid when using MQTT v3.1 or v3.1.1.
						See also the <option>--username</option> option.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--proxy</option></term>
				<listitem>
					<para>Specify a SOCKS5 proxy to connect through. "None" and
						"username" authentication types are supported. The
						<option>socks-url</option> must be of the form
						<option>socks5h://[username[:password]@]host[:port]</option>.
						The protocol prefix <option>socks5h</option> means that
						hostnames are resolved by the proxy. The symbols %25,
						%3A and %40 are URL decoded into %, : and @
						respectively, if present in the username or
						password.</para>
					<para>If username is not given, then no authentication is
						attempted. If the port is not given, then the default
						of 1080 is used.</para>
					<para>More SOCKS versions may be available in the future,
						depending on demand, and will use different protocol
						prefixes as described in <citerefentry>
							<refentrytitle>curl</refentrytitle>
							<manvolnum>1</manvolnum> </citerefentry>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--psk</option></term>
				<listitem>
					<para>Provide the hexadecimal (no leading 0x)
						pre-shared-key matching the one used on the broker to
						use TLS-PSK encryption support.
						<option>--psk-identity</option> must also be provided
						to enable TLS-PSK.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--psk-identity</option></term>
				<listitem>
					<para>The client identity to use with TLS-PSK support. This
						may be used instead of a username if the broker is
						configured to do so.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-q</option></term>
				<term><option>--qos</option></term>
				<listitem>
					<para>Specify the quality of service desired for the
					incoming messages, from 0, 1 and 2. Defaults to 0. See
					<citerefentry><refentrytitle>mqtt</refentrytitle><manvolnum>7</manvolnum></citerefentry>
					for more information on QoS.</para>
					<para>The QoS is identical for all topics subscribed to in
					a single instance of mosquitto_sub.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--quiet</option></term>
				<listitem>
					<para>If this argument is given, no runtime errors will be
					printed. This excludes any error messages given in case of
					invalid user input (e.g. using <option>--port</option> without a
					port).</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-R</option></term>
				<listitem>
					<para>If this argument is given, messages that are received
						that have the retain bit set will not be printed.
						Messages with retain set are "stale", in that it is not
						known when they were originally published. When
						subscribing to a wildcard topic there may be a large
						number of retained messages. This argument suppresses
						their display.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--remove-retained</option></term>
				<listitem>
					<para>If this argument is given, the when mosquitto_sub
						receives a message with the retained bit set, it will
						send a message to the broker to clear that retained
						message. This applies to all received messages except
						those that are filtered out by the <option>-T</option>
						option. This option still takes effect even if
						<option>-R</option> is used.  See also the
						<option>--retain-as-published</option> and
						<option>--retained-only</option> options.</para>

						<example title="remove-retained-example-1" label="1">
						<para>Remove all retained messages on the server,
							assuming we have access to do so, and then exit:</para>

						<programlisting language="config">
mosquitto_sub -t '#' --remove-retained --retained-only</programlisting>
						</example>

						<example title="remove-retained-example-2" label="2">
						<para>Remove a whole tree, with the exception of a
							single topic:</para>

						<programlisting language="config">
mosquitto_sub -t 'bbc/#' -T bbc/bbc1 --remove-retained</programlisting>
						</example>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--retained-only</option></term>
				<listitem>
					<para>If this argument is given, only messages that are
						received that have the retain bit set will be printed.
						Messages with retain set are "stale", in that it is not
						known when they were originally published. With this
						argument in use, the receipt of the first non-stale
						message will cause the client to exit. See also the
						<option>--retain-as-published</option> option.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--retain-as-published</option></term>
				<listitem>
					<para>If this argument is given, the subscriptions will
						have the "retain as published" option set. This means
						that the retain flag on an incoming message will be
						exactly as set by the publishing client, rather than
						indicating whether the message is fresh/stale.</para>
					<para>This option is not valid for MQTT v3.1/v3.1.1
						clients.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-S</option></term>
				<listitem>
					<para>Use SRV lookups to determine which host to connect
						to. Performs lookups to
						<option>_mqtt._tcp.&lt;host&gt;</option> when used in
						conjunction with <option>-h</option>, otherwise uses
						<option>_mqtt._tcp.&lt;local dns
							domain&gt;</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-t</option></term>
				<term><option>--topic</option></term>
				<listitem>
					<para>The MQTT topic to subscribe to. See
					<citerefentry><refentrytitle>mqtt</refentrytitle><manvolnum>7</manvolnum></citerefentry>
					for more information on MQTT topics.</para>
					<para>This option may be repeated to subscribe to multiple topics.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-T</option></term>
				<term><option>--filter-out</option></term>
				<listitem>
					<para>Suppress printing of topics that match the filter.
						This allows subscribing to a wildcard topic and only
						printing a partial set of the wildcard
						hierarchy.</para>
					<para>For example, subscribe to the BBC tree, but suppress output from Radio 3:</para>
					<itemizedlist mark="circle">
						<listitem><para>mosquitto_sub <literal>-t</literal>
								bbc/# <literal>-T</literal>
								bbc/radio3</para></listitem>
					</itemizedlist>
					<para>This option may be repeated to filter out multiple
						topics or topic trees.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--tls-alpn</option></term>
				<listitem>
					<para>Provide a protocol to use when connecting to a broker
						that has multiple protocols available on a single port,
						e.g. MQTT and WebSockets.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--tls-engine</option></term>
				<listitem>
					<para>A valid openssl engine id. These can be listed with
						openssl engine command.</para>
					<para>See also <option>--keyform</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--tls-engine-kpass-sha1</option></term>
				<listitem>
					<para>SHA1 of the private key password when using an TLS
						engine.  Some TLS engines such as the TPM engine may
						require the use of a password in order to be accessed.
						This option allows a hex encoded SHA1 hash of the
						password to the engine directly, instead of the user
						being prompted for the password.</para>
					<para>See also <option>--tls-engine</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--tls-version</option></term>
				<listitem>
					<para>Choose which TLS protocol version to use when
						communicating with the broker. Valid options are
						<option>tlsv1.3</option>, <option>tlsv1.2</option> and
						<option>tlsv1.1</option>. The default value is
						<option>tlsv1.2</option>. Must match the protocol
						version used by the broker.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-u</option></term>
				<term><option>--username</option></term>
				<listitem>
					<para>Provide a username to be used for authenticating with
						the broker. See also the <option>--pw</option>
						argument.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-U</option></term>
				<term><option>--unsubscribe</option></term>
				<listitem>
					<para>A topic that will be unsubscribed from. This may be
						used on its own or in conjunction with the
						<option>--topic</option> option and only makes sense
						when used in conjunction with
						<option>--clean-session</option>.</para>
					<para>If used with <option>--topic</option> then
						subscriptions will be processed before
						unsubscriptions.</para>
					<para>Note that it is only possible to unsubscribe from
						subscriptions that have previously been made. It is not
						possible to punch holes in wildcard subscriptions. For
						example, subscribing to <option>sensors/#</option> and
						then unsubscribing from
						<option>sensors/+/temperature</option> as shown below
						will still result in messages matching the
						<option>sensors/+/temperature</option> being delivered
						to the client.</para>
					<itemizedlist mark="circle">
						<listitem><para>mosquitto_sub <literal>-t</literal> sensors/# <literal>-U</literal> sensors/+/temperature <literal>-v</literal></para></listitem>
					</itemizedlist>

					<para>Note also that because retained messages are
						published by the broker on receipt of a SUBSCRIBE
						command, subscribing and unsubscribing to the same
						topic may result in messages being received at the
						client.</para>

					<para>This option may be repeated to unsubscribe from multiple topics.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-v</option></term>
				<term><option>--verbose</option></term>
				<listitem>
					<para>Print received messages verbosely. With this
					argument, messages will be printed as "topic payload". When
					this argument is not given, the messages are printed as
					"payload".</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-V</option></term>
				<term><option>--protocol-version</option></term>
				<listitem>
					<para>Specify which version of the MQTT protocol should be
						used when connecting to the remote broker. Can be
						<option>5</option>, <option>311</option>,
						<option>31</option>, or the more verbose
						<option>mqttv5</option>, <option>mqttv311</option>, or
						<option>mqttv31</option>.
						Defaults to <option>311</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>-W</option></term>
				<listitem>
					<para>Provide a timeout as an integer number of seconds.
						mosquitto_sub will stop processing messages and
						disconnect after this number of seconds has
						passed. The timeout starts just after the client has
						connected to the broker.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--will-payload</option></term>
				<listitem>
					<para>Specify a message that will be stored by the broker
					and sent out if this client disconnects unexpectedly. This
					must be used in conjunction with <option>--will-topic</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--will-qos</option></term>
				<listitem>
					<para>The QoS to use for the Will. Defaults to 0. This must
					be used in conjunction with <option>--will-topic</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--will-retain</option></term>
				<listitem>
					<para>If given, if the client disconnects unexpectedly the
					message sent out will be treated as a retained message.
					This must be used in conjunction with <option>--will-topic</option>.</para>
				</listitem>
			</varlistentry>
			<varlistentry>
				<term><option>--will-topic</option></term>
				<listitem>
					<para>The topic on which to send a Will, in the event that
					the client disconnects unexpectedly.</para>
				</listitem>
			</varlistentry>
		</variablelist>
	</refsect1>

	<refsect1 id='outputformat'>
		<title>Output format</title>
		<para>There are three ways of formatting the output from mosquitto_sub.
			In all cases a new-line character is appended for each message
			received unless the <option>-N</option> argument is passed to
			mosquitto_sub.</para>
		<para>Payload-only is the default output format and will
			print the payload exactly as it is received.</para>
		<para>Verbose mode is activated with <option>-v</option> and prints the
			message topic and the payload, separated by a space.</para>
		<para>The final option is formatted output, which allows the user to
			define a custom output format.  The behaviour is controlled with
			the <option>-F format-string</option> option. The format string is
			a free text string where interpreted sequences are replaced by
			different parameters. The available interpreted sequences are
			described below.</para>
		<para>Three characters are used to start an interpreted sequence:
			<option>%</option>, <option>@</option> and <option>\</option>.
			Sequences starting with <option>%</option> are either parameters
			related to the MQTT message being printed, or are helper sequences
			to avoid the need to type long date format strings for example.
			Sequences starting with <option>@</option> are passed to the
			<citerefentry><refentrytitle>strftime</refentrytitle><manvolnum>3</manvolnum></citerefentry>
			function (with the @ replaced with a % - note that only the
			character immediately after the @ is passed to strftime). This
			allows the construction of a wide variety of time based outputs.
			The output options for strftime vary from platform to platform, so
			please check what is available for your platform. mosquitto_sub
			does provide one extension to strftime which is
			<option>@N</option>, which can be used to obtain the number of
			nanoseconds passed in the current second. The resolution of this
			option varies depending on the platform. The final sequence
			character is <option>\</option>, which is used to input some
			characters that would otherwise be difficult to enter.</para>

		<refsect2>
			<title>MQTT related parameters</title>
			<itemizedlist mark="circle">
				<listitem><para><option>%%</option> a literal %.</para></listitem>
				<listitem><para><option>%l</option> the length of the payload in bytes.</para></listitem>
				<listitem><para><option>%m</option> the message id (only relevant for messages with QoS>0).</para></listitem>
				<listitem><para><option>%p</option> the payload raw bytes (may produce non-printable characters depending on the payload).</para></listitem>
				<listitem><para><option>%q</option> the message QoS.</para></listitem>
				<listitem><para><option>%r</option> the retained flag for the message.</para></listitem>
				<listitem><para><option>%t</option> the message topic.</para></listitem>
				<listitem><para><option>%x</option> the payload with each byte as a hexadecimal number (lower case).</para></listitem>
				<listitem><para><option>%X</option> the payload with each byte as a hexadecimal number (upper case).</para></listitem>
			</itemizedlist>
		</refsect2>

		<refsect2>
			<title>Helpers</title>
			<itemizedlist mark="circle">
				<listitem><para><option>%I</option> ISO-8601 format date and time, e.g. 2016-08-10T09:47:38+0100</para></listitem>
				<listitem><para><option>%j</option> JSON output of message
						parameters and timestamp, with a quoted and escaped
						payload. For example
						<code>{"tst":1470825369,"topic":"greeting","qos":0,"retain":0,"payload":"hello
							world"}</code></para></listitem>
				<listitem><para><option>%J</option> JSON output of message
						parameters and timestamp, with a non-quoted and
						non-escaped payload - this means the payload must
						itself be valid JSON. For example:
						<code>{"tst":1470825369,"topic":"foo","qos":0,"retain":0,"payload":{"temperature":27.0,"humidity":57}}</code>.</para></listitem>
				<listitem><para><option>%I</option> ISO-8601 format date and time, e.g. 2016-08-10T09:47:38+0100</para></listitem>
				<listitem><para><option>%U</option> Unix timestamp with nanoseconds, e.g. 1470818943.786368637</para></listitem>
			</itemizedlist>
		</refsect2>

		<refsect2>
			<title>Time related parameters</title>
			<itemizedlist mark="circle">
				<listitem><para><option>@@</option> a literal @.</para></listitem>
				<listitem><para><option>@X</option> pass the character represented
						by <option>X</option> to the strftime function as
						<option>%X</option>. The options supported are platform
						dependent.</para></listitem>
				<listitem><para><option>@N</option> the number of nanoseconds that
						have passed in the current second, with varying timing
						resolution depending on platform.</para></listitem>
			</itemizedlist>
		</refsect2>

		<refsect2>
			<title>Escape characters</title>
			<itemizedlist mark="circle">
				<listitem><para><option>\\</option> a literal \.</para></listitem>
				<listitem><para><option>\0</option> a null character. Can be used
						to separate different parameters that may contain spaces
						(e.g. topic, payload) so that processing with tools such as
						<citerefentry><refentrytitle>xargs</refentrytitle><manvolnum>1</manvolnum></citerefentry>
						is easier.</para></listitem>
				<listitem><para><option>\a</option> alert/bell.</para></listitem>
				<listitem><para><option>\e</option> the escape sequence, which can
						be used with ANSI colour codes to provide coloured output
						for example.</para></listitem>
				<listitem><para><option>\n</option> end of line.</para></listitem>
				<listitem><para><option>\r</option> carriage return.</para></listitem>
				<listitem><para><option>\t</option> horizontal tab.</para></listitem>
				<listitem><para><option>\v</option> vertical tab.</para></listitem>
			</itemizedlist>
		</refsect2>
	</refsect1>

	<refsect1>
		<title>Wills</title>
		<para>mosquitto_sub can register a message with the broker that will be
		sent out if it disconnects unexpectedly. See
		<citerefentry><refentrytitle>mqtt</refentrytitle><manvolnum>7</manvolnum></citerefentry>
		for more information.</para>
		<para>The minimum requirement for this is to use <option>--will-topic</option> to
		specify which topic the will should be sent out on. This will result in
		a non-retained, zero length message with QoS 0.</para>
		<para>Use the <option>--will-retain</option>, <option>--will-payload</option> and <option>--will-qos</option> arguments to
		modify the other will parameters.</para>
	</refsect1>

	<refsect1 id='properties'>
		<title>Properties</title>
		<para>The <option>-D</option> / <option>--property</option> option
			allows adding properties to different stages of the mosquitto_sub
			run. The properties supported for each command are as
			follows:</para>

		<refsect2>
			<title>Connect</title>
			<itemizedlist>
				<listitem><para><option>authentication-data</option> (binary data - note treated as a string in mosquitto_sub)</para></listitem>
				<listitem><para><option>authentication-method</option> (UTF-8 string pair)</para></listitem>
				<listitem><para><option>maximum-packet-size</option> (32-bit unsigned integer)</para></listitem>
				<listitem><para><option>receive-maximum</option> (16-bit unsigned integer)</para></listitem>
				<listitem><para><option>request-problem-information</option> (8-bit unsigned integer)</para></listitem>
				<listitem><para><option>request-response-information</option> (8-bit unsigned integer)</para></listitem>
				<listitem><para><option>session-expiry-interval</option> (32-bit unsigned integer)</para></listitem>
				<listitem><para><option>topic-alias-maximum</option> (16-bit unsigned integer)</para></listitem>
				<listitem><para><option>user-property</option> (UTF-8 string pair)</para></listitem>
			</itemizedlist>
		</refsect2>

		<refsect2>
			<title>Subscribe</title>
			<itemizedlist>
				<listitem><para><option>user-property</option> (UTF-8 string pair)</para></listitem>
			</itemizedlist>
		</refsect2>

		<refsect2>
			<title>Unsubscribe</title>
			<itemizedlist>
				<listitem><para><option>user-property</option> (UTF-8 string pair)</para></listitem>
			</itemizedlist>
		</refsect2>

		<refsect2>
			<title>Disconnect</title>
			<itemizedlist>
				<listitem><para><option>session-expiry-interval</option> (32-bit unsigned integer)</para></listitem>
				<listitem><para><option>user-property</option> (UTF-8 string pair)</para></listitem>
			</itemizedlist>
		</refsect2>

		<refsect2>
			<title>Will properties</title>
			<itemizedlist>
				<listitem><para><option>content-type</option> (UTF-8 string)</para></listitem>
				<listitem><para><option>correlation-data</option> (binary data - note treated as a string in mosquitto_sub)</para></listitem>
				<listitem><para><option>message-expiry-interval</option> (32-bit unsigned integer)</para></listitem>
				<listitem><para><option>payload-format-indicator</option> (8-bit unsigned integer)</para></listitem>
				<listitem><para><option>response-topic</option> (UTF-8 string)</para></listitem>
				<listitem><para><option>user-property</option> (UTF-8 string pair)</para></listitem>
				<listitem><para><option>will-delay-interval</option> (32-bit unsigned integer)</para></listitem>
			</itemizedlist>
		</refsect2>
	</refsect1>

	<refsect1>
		<title>Examples</title>
		<para>Note that these really are examples - the subscriptions will work
		if you run them as shown, but there must be something publishing
		messages on those topics for you to receive anything.</para>
		<para>Subscribe to temperature information on localhost with QoS 1:</para>
		<itemizedlist mark="circle">
			<listitem><para>mosquitto_sub <literal>-t</literal> sensors/temperature <literal>-q</literal> 1</para></listitem>
		</itemizedlist>
		<para>Subscribe to hard drive temperature updates on multiple
		machines/hard drives. This expects each machine to be publishing its
		hard drive temperature to
		sensors/machines/HOSTNAME/temperature/HD_NAME.</para>
		<itemizedlist mark="circle">
			<listitem><para>mosquitto_sub <literal>-t</literal> sensors/machines/+/temperature/+</para></listitem>
		</itemizedlist>
		<para>Subscribe to all broker status messages:</para>
		<itemizedlist mark="circle">
			<listitem><para>mosquitto_sub <literal>-v</literal> <literal>-t</literal> \$SYS/#</para></listitem>
		</itemizedlist>

		<para>Specify the output format as "ISO-8601 date : topic : payload in hex"</para>
		<itemizedlist mark="circle">
			<listitem><para>mosquitto_sub <literal>-F '@Y-@m-@dT@H:@M:@S@z : %t : %x'</literal> <literal>-t</literal> '#'</para></listitem>
		</itemizedlist>

		<para>Specify the output format as "seconds since epoch.nanoseconds : retained flag : qos : mid : payload length"</para>
		<itemizedlist mark="circle">
			<listitem><para>mosquitto_sub <literal>-F '%@s.@N : %r : %q : %m : %l'</literal> <literal>-q 2</literal> <literal>-t</literal> '#'</para></listitem>
		</itemizedlist>

		<para>Topic and payload output, but with colour where supported.</para>
		<itemizedlist mark="circle">
			<listitem><para>mosquitto_sub <literal>-F '\e[92m%t \e[96m%p\e[0m'</literal> <literal>-q 2</literal> <literal>-t</literal> '#'</para></listitem>
		</itemizedlist>
	</refsect1>

	<refsect1>
		<title>Files</title>
		<variablelist>
			<varlistentry>
				<term><filename>$XDG_CONFIG_HOME/mosquitto_sub</filename></term>
				<term><filename>$HOME/.config/mosquitto_sub</filename></term>
				<listitem>
					<para>Configuration file for default options.</para>
				</listitem>
			</varlistentry>
		</variablelist>
	</refsect1>

	<refsect1>
		<title>Bugs</title>
		<para><command>mosquitto</command> bug information can be found at
			<ulink url="https://github.com/eclipse/mosquitto/issues"/></para>
	</refsect1>

	<refsect1>
		<title>See Also</title>
		<simplelist type="inline">
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mqtt-7.html">mqtt</link></refentrytitle>
					<manvolnum>7</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mosquitto_pub-1.html">mosquitto_pub</link></refentrytitle>
					<manvolnum>1</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mosquitto_rr-1.html">mosquitto_rr</link></refentrytitle>
					<manvolnum>1</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mosquitto-8.html">mosquitto</link></refentrytitle>
					<manvolnum>8</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="libmosquitto-3.html">libmosquitto</link></refentrytitle>
					<manvolnum>3</manvolnum>
				</citerefentry>
			</member>
			<member>
				<citerefentry>
					<refentrytitle><link xlink:href="mosquitto-tls-7.html">mosquitto-tls</link></refentrytitle>
					<manvolnum>7</manvolnum>
				</citerefentry>
			</member>
		</simplelist>
	</refsect1>

	<refsect1>
		<title>Author</title>
		<para>Roger Light <email>roger@atchoo.org</email></para>
	</refsect1>
</refentry>
