varlinkctl - Man Page

varlinkctl [Options...] info ADDRESS

varlinkctl [Options...] list-interfaces ADDRESS

varlinkctl [Options...] introspect ADDRESS INTERFACE

varlinkctl [Options...] call ADDRESS METHOD [ARGUMENTS]

varlinkctl [Options...] validate-idl [FILE]

varlinkctl may be used to introspect and invoke Varlink^[1] services.

Services are referenced by one of the following:

• 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.)

For convenience these two simpler (redundant) service address syntaxes are also 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. "./").

The following commands are understood:

info ADDRESS

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.

list-interfaces ADDRESS

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

Added in version 255.

introspect ADDRESS INTERFACE

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 ADDRESS METHOD [ARGUMENTS]

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.

validate-idl [FILE]

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.

help

Show command syntax help.

Added in version 255.

The following options are understood:

--more

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.

--collect

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.

--oneway

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.

--json=MODE

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.

-j

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.

--no-pager

Do not pipe output into a pager.

-h,  --help

Print a short help text and exit.

--version

Print a short version string and exit.

Example 1. Investigating a Service

The following three commands inspect the "io.systemd.Resolve" service implemented by systemd-resolved.service(8), listing general service information and implemented interfaces, and then displaying the interface definition of its primary interface:

$ 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,
        ...

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

Example 2. Invoking a Method

The following command resolves a hostname via systemd-resolved.service(8)'s ResolveHostname method call.

$ 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
}

Example 3. Investigating a Service Executable

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

# 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"}'
{}

busctl(1), Varlink^[1]

1.

Varlink
https://varlink.org/

busctl(1), systemd.directives(7), systemd.index(7).