NAME

       babeltrace2-source.text.dmesg - Babeltrace 2's Linux kernel ring buffer source component
       class

DESCRIPTION

       A Babeltrace 2 source.text.dmesg message iterator reads the lines of a Linux kernel ring
       buffer, as printed by the dmesg(1) tool, and emits corresponding event messages.

           Linux kernel ring buffer
           lines (file or standard input)
             |
             |   +----------------+
             |   | src.text.dmesg |
             '-->|                |
                 |            out @--> Messages (single stream)
                 +----------------+

       See babeltrace2-intro(7) to learn more about the Babeltrace 2 project and its core
       concepts.

       A source.text.dmesg message iterator names the events it creates string. Each event
       contain a single payload string field named str which contains the corresponding ring
       buffer line.

       By default, a source.text.dmesg message iterator reads the lines of the standard input
       stream. You can make the message iterator read the lines of a text file instead with the
       path parameter.

       By default, the message iterator tries to extract the timestamps of the kernel ring buffer
       lines and use them as the created events’s timestamps. A typical dmesg(1) line looks like
       this:

           [87166.510937] PM: Finishing wakeup.

       The [87166.510937] part is the timestamp to extract. When this information is available,
       the component creates a clock class which does NOT have the Unix epoch as its origin.

       You can make the message iterator not extract timestamps from lines with the no-extract-
       timestamp parameter.

           Note
           It is possible that the output of dmesg(1) contains unsorted lines, that is, their
           timestamps go back in time. You can see this with the --show-delta option of dmesg(1):
           some time differences can be negative.

           This is due to a 2019 change (see <https://lwn.net/Articles/780556/>) to the kernel’s
           ring buffer API.

           As of this version, a source.text.dmesg message iterator requires that the input
           kernel ring buffer lines be sorted by timestamp (when they have timestamps), failing
           otherwise.

INITIALIZATION PARAMETERS

       no-extract-timestamp=VAL [optional boolean]
           If VAL is true, then do NOT extract timestamps from the kernel ring buffer lines: set
           the created event’s payload’s str field to the whole line, including any timestamp
           prefix.

           Default: false.

       path=PATH [optional string]
           Read the kernel ring buffer lines from the file PATH instead of the standard input
           stream.

PORTS

           +----------------+
           | src.text.dmesg |
           |                |
           |            out @
           +----------------+

   Output
       out
           Single output port.

BUGS

       If you encounter any issue or usability problem, please report it on the Babeltrace bug
       tracker (see <https://bugs.lttng.org/projects/babeltrace>).

RESOURCES

       The Babeltrace project shares some communication channels with the LTTng project (see
       <https://lttng.org/>).

       •   Babeltrace website (see <https://babeltrace.org/>)

       •   Mailing list (see <https://lists.lttng.org>) for support and development: lttng-
           dev@lists.lttng.org

       •   IRC channel (see <irc://irc.oftc.net/lttng>): #lttng on irc.oftc.net

       •   Bug tracker (see <https://bugs.lttng.org/projects/babeltrace>)

       •   Git repository (see <https://git.efficios.com/?p=babeltrace.git>)

       •   GitHub project (see <https://github.com/efficios/babeltrace>)

       •   Continuous integration (see <https://ci.lttng.org/view/Babeltrace/>)

       •   Code review (see <https://review.lttng.org/q/project:babeltrace>)

AUTHORS

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

       The current project maintainer is Jérémie Galarneau
       <mailto:jeremie.galarneau@efficios.com>.

COPYRIGHT

       This component class is part of the Babeltrace 2 project.

       Babeltrace is distributed under the MIT license (see
       <https://opensource.org/licenses/MIT>).

SEE ALSO

       babeltrace2-plugin-text(7), babeltrace2-intro(7)

                                                                             BABELTRACE2-SOURCE()