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BABELTRACE2-QUERY-(7) Babeltrace 2 manual BABELTRACE2-QUERY-(7) - Babeltrace 2's support info query object

The Babeltrace 2 query object indicates, for a given source component class, whether or not its instance can handle a given input, and if so, what’s the confidence of this support.

Said input can be a simple string, an existing file path, or an existing directory path. Components which expect some form of URI can handle a string input, while components which expect an existing file or directory can handle a file/directory path input.

When the source component class’s query method replies that its component can handle a given input, it can also specify the name of a group in which to put that input. All the inputs of a given group, for a given component class, should be passed when instantiating the component class as its inputs initialization parameter (array of strings).

The babeltrace2-convert(1) command queries this object from specific source component classes to find the most appropriate for a given non-option argument.

input=INPUT [string]
Check input INPUT.

Depending on the type parameter, this is a simple string, a file path, or a directory path.

type=(string | file | directory) [string]

Input type, one of:


input parameter is a simple string.


input parameter is a file path.


input parameter is a directory path.

It is expected that the query method does not recurse into this directory: the result object indicates whether or not the component class supports this specific directory (input).

The result object can be one of:
•A simple real value which is the weight, between 0 and 1, of the support by the component class for the given input.

A weight of 0 means the input is unsupported while a weight of 1 means it’s fully supported. Any value in between shows how confident the component class is about the support of the given input.

•A map with a weight and an optional group name.

When it’s a map, the expected entries are:

group=GROUP-NAME [optional string]

Put the given input into a group named GROUP-NAME for this component class.

If this entry is missing, then the given input gets its own, unique group.

weight=WEIGHT [real]

Weight, between 0 and 1, of the support by the component class for the given input.

The semantics are the same as when the result object is a simple real value.

Example 1. String input.
input: net://relayd177/host/node23/active
type: string

Example 2. File path input.

input: /home/user/traces/2019-08-26/
type: file

Example 3. Simple weight (unique group).

Example 4. Weight and specific group.

group: 63a4b7e5-37f0-4254-a048-a0cff9e5b761
weight: 0.75

Example 5. Weight within a map (unique group).

weight: 0.6

If you encounter any issue or usability problem, please report it on the Babeltrace bug tracker (see

The Babeltrace project shares some communication channels with the LTTng project (see
•Babeltrace website (see
•Mailing list (see for support and development:
•IRC channel (see <irc://>): #lttng on
•Continuous integration (see

The Babeltrace 2 project is the result of hard work by many regular developers and occasional contributors.

The current project maintainer is Jérémie Galarneau <>.

This query object is part of the Babeltrace 2 project.

Babeltrace is distributed under the MIT license (see

babeltrace2-intro(7), babeltrace2-query(1), babeltrace2-convert(1)
14 September 2019 Babeltrace 2.0.3