varlinkctl — Introspect with and invoke Varlink services
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 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:
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.
ADDRESS¶Show list of interfaces implemented by the specified service. Expects a service address in one of the formats described above.
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.
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.
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.
Show command syntax help.
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.
--collect¶This is similar to --more but collects all responses in a JSON
array, and prints it, rather than in JSON_SEQ mode.
--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.
--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".
-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.
--no-pager¶Do not pipe output into a pager.
-h, --help¶--version¶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"}'
{}