--- name: "babeltrace2-source.text.dmesg" section: "7" platform: "linux" package: "babeltrace2" version: "2.1.1-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/babeltrace2-source.text.dmesg" --- # babeltrace2-source.text.dmesg(7) Babeltrace 2: Linux kernel ring buffer source component class ## NAME babeltrace2-source.text.dmesg - Babeltrace 2: 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)](/dmesg/1.md) 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)](/babeltrace2-intro/7.md) 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 timestamps of the created events. A typical [**dmesg**(1)](/dmesg/1.md) 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’s possible that the output of [**dmesg**(1)](/dmesg/1.md) contains unsorted lines, that is, their timestamps go back in time. You can see this with the **--show-delta** option of [**dmesg**(1)](/dmesg/1.md): some time differences can be negative. This is due to a 2019 change (see \) to the API of the kernel ring buffer. 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 **str** payload field of the created event 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 \). ## RESOURCES The Babeltrace project shares some communication channels with the LTTng project (see \). • Babeltrace website (see \) • Mailing list (see \) for support and development: **lttng-dev@lists.lttng.org** • IRC channel (see \): **#lttng** on **irc.oftc.net** • Bug tracker (see \) • Git repository (see \) • GitHub project (see \) • Continuous integration (see \) • Code review (see \) ## 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 \. ## COPYRIGHT This component class is part of the Babeltrace 2 project. Babeltrace is distributed under the MIT license (see \). ## SEE ALSO [**babeltrace2-plugin-text**(7)](/babeltrace2-plugin-text/7.md), [**babeltrace2-intro**(7)](/babeltrace2-intro/7.md)