1BABELTRACE2-SOURCE()                                      BABELTRACE2-SOURCE()
2
3
4

NAME

6       babeltrace2-source.text.dmesg - Babeltrace 2's Linux kernel ring buffer
7       source component class
8

DESCRIPTION

10       A Babeltrace 2 source.text.dmesg message iterator reads the lines of a
11       Linux kernel ring buffer, as printed by the dmesg(1) tool, and emits
12       corresponding event messages.
13
14           Linux kernel ring buffer
15           lines (file or standard input)
16             |
17             |   +----------------+
18             |   | src.text.dmesg |
19             '-->|                |
20                 |            out @--> Messages (single stream)
21                 +----------------+
22
23       See babeltrace2-intro(7) to learn more about the Babeltrace 2 project
24       and its core concepts.
25
26       A source.text.dmesg message iterator names the events it creates
27       string. Each event contain a single payload string field named str
28       which contains the corresponding ring buffer line.
29
30       By default, a source.text.dmesg message iterator reads the lines of the
31       standard input stream. You can make the message iterator read the lines
32       of a text file instead with the path parameter.
33
34       By default, the message iterator tries to extract the timestamps of the
35       kernel ring buffer lines and use them as the created events’s
36       timestamps. A typical dmesg(1) line looks like this:
37
38           [87166.510937] PM: Finishing wakeup.
39
40       The [87166.510937] part is the timestamp to extract. When this
41       information is available, the component creates a clock class which
42       does NOT have the Unix epoch as its origin.
43
44       You can make the message iterator not extract timestamps from lines
45       with the no-extract-timestamp parameter.
46
47           Note
48           It is possible that the output of dmesg(1) contains unsorted lines,
49           that is, their timestamps go back in time. You can see this with
50           the --show-delta option of dmesg(1): some time differences can be
51           negative.
52
53           This is due to a 2019 change (see
54           <https://lwn.net/Articles/780556/>) to the kernel’s ring buffer
55           API.
56
57           As of this version, a source.text.dmesg message iterator requires
58           that the input kernel ring buffer lines be sorted by timestamp
59           (when they have timestamps), failing otherwise.
60

INITIALIZATION PARAMETERS

62       no-extract-timestamp=yes [optional boolean]
63           Do NOT extract timestamps from the kernel ring buffer lines: set
64           the created event’s payload’s str field to the whole line,
65           including any timestamp prefix.
66
67       path=PATH [optional string]
68           Read the kernel ring buffer lines from the file PATH instead of the
69           standard input stream.
70

PORTS

72           +----------------+
73           | src.text.dmesg |
74           |                |
75           |            out @
76           +----------------+
77
78   Output
79       out
80           Single output port.
81

BUGS

83       If you encounter any issue or usability problem, please report it on
84       the Babeltrace bug tracker (see
85       <https://bugs.lttng.org/projects/babeltrace>).
86

RESOURCES

88       The Babeltrace project shares some communication channels with the
89       LTTng project (see <https://lttng.org/>).
90
91       •   Babeltrace website (see <https://babeltrace.org/>)
92
93       •   Mailing list (see <https://lists.lttng.org>) for support and
94           development: lttng-dev@lists.lttng.org
95
96       •   IRC channel (see <irc://irc.oftc.net/lttng>): #lttng on
97           irc.oftc.net
98
99       •   Bug tracker (see <https://bugs.lttng.org/projects/babeltrace>)
100
101       •   Git repository (see <https://git.efficios.com/?p=babeltrace.git>)
102
103       •   GitHub project (see <https://github.com/efficios/babeltrace>)
104
105       •   Continuous integration (see
106           <https://ci.lttng.org/view/Babeltrace/>)
107
108       •   Code review (see <https://review.lttng.org/q/project:babeltrace>)
109

AUTHORS

111       The Babeltrace 2 project is the result of hard work by many regular
112       developers and occasional contributors.
113
114       The current project maintainer is Jérémie Galarneau
115       <mailto:jeremie.galarneau@efficios.com>.
116

118       This component class is part of the Babeltrace 2 project.
119
120       Babeltrace is distributed under the MIT license (see
121       <https://opensource.org/licenses/MIT>).
122

SEE ALSO

124       babeltrace2-plugin-text(7), babeltrace2-intro(7)
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128                                                          BABELTRACE2-SOURCE()
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