•A Varlink service reference starting with the "unix:" string, followed by an absolute AF_UNIX socket path, or by "@" and an arbitrary string (the latter for referencing sockets in the abstract namespace).

•A Varlink service reference starting with the "exec:" string, followed by an absolute path of a binary to execute.

•A Varlink service reference starting with the "ssh:" string, followed by an SSH host specification, followed by ":", followed by an absolute AF_UNIX socket path. (This requires OpenSSH 9.4 or newer on the server side, abstract namespace sockets are not supported.)

•A file system path to an AF_UNIX socket, either absolute (i.e. begins with "/") or relative (in which case it must begin with "./").

•A file system path to an executable, either absolute or relative (as above, must begin with "/", resp. "./").

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.

Added in version 255.

Show list of interfaces implemented by the specified service. Expects a service address in one of the formats described above.

Added in version 255.

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.

Added in version 255.

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 "{}".

The reply parameters are written as JSON object to STDOUT.

Added in version 255.

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.

Added in version 255.

Show command syntax help.

Added in version 255.

When used with call: expect multiple method replies. If this flag is set the method call is sent with the more 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.

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

Added in version 255.

This is similar to --more but collects all responses in a JSON array, and prints it, rather than in JSON_SEQ mode.

Added in version 256.

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

Added in version 255.

Selects the JSON output formatting, one of "pretty" (for nicely indented, colorized output) or "short" (for terse output with minimal whitespace and no newlines), defaults to "short".

Added in version 255.

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

Added in version 255.

Do not pipe output into a pager.

Print a short help text and exit.

Print a short version string and exit.

$ 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,


        ...

$ 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
}

# 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"}'
{}