systemd/man/varlinkctl.xml

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<refentry id="varlinkctl"
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>varlinkctl</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>varlinkctl</refentrytitle>
    <manvolnum>1</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>varlinkctl</refname>
    <refpurpose>Introspect with and invoke Varlink services</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">info</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">list-interfaces</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">introspect</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
      <arg choice="plain"><replaceable>INTERFACE</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">call</arg>
      <arg choice="plain"><replaceable>ADDRESS</replaceable></arg>
      <arg choice="plain"><replaceable>METHOD</replaceable></arg>
      <arg choice="opt"><replaceable>ARGUMENTS</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>varlinkctl</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">validate-idl</arg>
      <arg choice="opt"><replaceable>FILE</replaceable></arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><command>varlinkctl</command> may be used to introspect and invoke <ulink
    url="https://varlink.org/">Varlink</ulink> services.</para>

    <para>Services are referenced by one of the following:</para>

    <itemizedlist>
      <listitem><para>A Varlink service reference starting with the <literal>unix:</literal> string, followed
      by an absolute <constant>AF_UNIX</constant> socket path, or by <literal>@</literal> and an arbitrary string
      (the latter for referencing sockets in the abstract namespace).</para></listitem>

      <listitem><para>A Varlink service reference starting with the <literal>exec:</literal> string, followed
      by an absolute path of a binary to execute.</para></listitem>

      <listitem><para>A Varlink service reference starting with the <literal>ssh:</literal> string, followed
      by an SSH host specification, followed by <literal>:</literal>, followed by an absolute
      <constant>AF_UNIX</constant> socket path. (This requires OpenSSH 9.4 or newer on the server side,
      abstract namespace sockets are not supported.)</para></listitem>
    </itemizedlist>

    <para>For convenience these two simpler (redundant) service address syntaxes are also supported:</para>

    <itemizedlist>
      <listitem><para>A file system path to an <constant>AF_UNIX</constant> socket, either absolute
      (i.e. begins with <literal>/</literal>) or relative (in which case it must begin with
      <literal>./</literal>).</para></listitem>

      <listitem><para>A file system path to an executable, either absolute or relative (as above, must begin
      with <literal>/</literal>, resp. <literal>./</literal>).</para></listitem>
    </itemizedlist>
  </refsect1>

  <refsect1>
    <title>Commands</title>

    <para>The following commands are understood:</para>

    <variablelist>
      <varlistentry>
        <term><command>info</command> <replaceable>ADDRESS</replaceable></term>

        <listitem><para>Show brief information about the specified service, including vendor name and list of
        implemented interfaces. Expects a service address in one of the formats described above.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>list-interfaces</command> <replaceable>ADDRESS</replaceable></term>

        <listitem><para>Show list of interfaces implemented by the specified service. Expects a service
        address in one of the formats described above.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>introspect</command> <replaceable>ADDRESS</replaceable> <replaceable>INTERFACE</replaceable></term>

        <listitem><para>Show interface definition of the specified interface provided by the specified
        service. Expects a service address in one of the formats described above and a Varlink interface
        name.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>call</command> <replaceable>ADDRESS</replaceable> <replaceable>METHOD</replaceable> [<replaceable>ARGUMENTS</replaceable>]</term>

        <listitem><para>Call the specified method of the specified service. Expects a service address in the
        format described above, a fully qualified Varlink method name, and a JSON arguments object. If the
        arguments object is not specified, it is read from STDIN instead. To pass an empty list of
        parameters, specify the empty object <literal>{}</literal>.</para>

        <para>The reply parameters are written as JSON object to STDOUT.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>validate-idl</command> [<replaceable>FILE</replaceable>]</term>

        <listitem><para>Reads a Varlink interface definition file, parses and validates it, then outputs it
        with syntax highlighting. This checks for syntax and internal consistency of the interface. Expects a
        file name to read the interface definition from. If omitted reads the interface definition from
        STDIN.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><command>help</command></term>

        <listitem><para>Show command syntax help.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>The following options are understood:</para>

    <variablelist>
      <varlistentry>
        <term><option>--more</option></term>

        <listitem><para>When used with <command>call</command>: expect multiple method replies. If this flag is
        set the method call is sent with the <constant>more</constant> flag set, which tells the service to
        generate multiple replies, if needed. The command remains running until the service sends a reply
        message that indicates it is the last in the series. This flag should be set only for method calls
        that support this mechanism.</para>

        <para>If this mode is enabled output is automatically switched to JSON-SEQ mode, so that individual
        reply objects can be easily discerned.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--collect</option></term>

        <listitem><para>This is similar to <option>--more</option> but collects all responses in a JSON
        array, and prints it, rather than in JSON_SEQ mode.</para>

        <xi:include href="version-info.xml" xpointer="v256"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--oneway</option></term>

        <listitem><para>When used with <command>call</command>: do not expect a method reply. If this flag
        is set the method call is sent with the <constant>oneway</constant> flag set (the command exits
        immediately after), which tells the service not to generate a reply.</para>

        <xi:include href="version-info.xml" xpointer="v255"/></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--json=<replaceable>MODE</replaceable></option></term>

        <listitem>
          <para>Selects the JSON output formatting, one of <literal>pretty</literal> (for nicely indented,
          colorized output) or <literal>short</literal> (for terse output with minimal whitespace and no
          newlines), defaults to <literal>short</literal>.</para>

        <xi:include href="version-info.xml" xpointer="v255"/>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-j</option></term>

        <listitem>
          <para>Equivalent to <option>--json=pretty</option> when invoked interactively from a terminal. Otherwise
          equivalent to <option>--json=short</option>, in particular when the output is piped to some other
          program.</para>

        <xi:include href="version-info.xml" xpointer="v255"/>
        </listitem>
      </varlistentry>

      <xi:include href="standard-options.xml" xpointer="no-pager" />
      <xi:include href="standard-options.xml" xpointer="help" />
      <xi:include href="standard-options.xml" xpointer="version" />
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Examples</title>

    <example>
      <title>Investigating a Service</title>

      <para>The following three commands inspect the <literal>io.systemd.Resolve</literal> service
      implemented by
      <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      listing general service information and implemented interfaces, and then displaying the interface
      definition of its primary interface:</para>

      <programlisting>$ varlinkctl info /run/systemd/resolve/io.systemd.Resolve
    Vendor: The systemd Project
   Product: systemd (systemd-resolved)
   Version: 254 (254-1522-g4790521^)
       URL: https://systemd.io/
Interfaces: io.systemd
            io.systemd.Resolve
            org.varlink.service
$ varlinkctl list-interfaces /run/systemd/resolve/io.systemd.Resolve
io.systemd
io.systemd.Resolve
org.varlink.service
$ varlinkctl introspect /run/systemd/resolve/io.systemd.Resolve io.systemd.Resolve
interface io.systemd.Resolve
type ResolvedAddress(
        ifindex: ?int,
        …</programlisting>

    <para>(Interface definition has been truncated in the example above, in the interest of brevity.)</para>
    </example>

    <example>
      <title>Invoking a Method</title>

      <para>The following command resolves a hostname via <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s <function>ResolveHostname</function>  method call.</para>

      <programlisting>$ varlinkctl call /run/systemd/resolve/io.systemd.Resolve io.systemd.Resolve.ResolveHostname '{"name":"systemd.io","family":2}' -j
{
        "addresses" : [
                {
                        "ifindex" : 2,
                        "family" : 2,
                        "address" : [
                                185,
                                199,
                                111,
                                153
                        ]
                }
        ],
        "name" : "systemd.io",
        "flags" : 1048577
}</programlisting>
    </example>

    <example>
      <title>Investigating a Service Executable</title>

      <para>The following command inspects the <filename>/usr/lib/systemd/systemd-pcrextend</filename>
      executable and the IPC APIs it provides. It then invokes a method on it:</para>

      <programlisting># varlinkctl info /usr/lib/systemd/systemd-pcrextend
    Vendor: The systemd Project
   Product: systemd (systemd-pcrextend)
   Version: 254 (254-1536-g97734fb)
       URL: https://systemd.io/
Interfaces: io.systemd
            io.systemd.PCRExtend
            org.varlink.service
# varlinkctl introspect /usr/lib/systemd/systemd-pcrextend io.systemd.PCRExtend
interface io.systemd.PCRExtend

method Extend(
        pcr: int,
        text: ?string,
        data: ?string
) -> ()
# varlinkctl call /usr/lib/systemd/systemd-pcrextend io.systemd.PCRExtend.Extend '{"pcr":15,"text":"foobar"}'
{}</programlisting>
    </example>

  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para><simplelist type="inline">
      <member><citerefentry><refentrytitle>busctl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
      <member><ulink url="https://varlink.org/">Varlink</ulink></member>
    </simplelist></para>
  </refsect1>
</refentry>