For example, consider the following commands:
[role="term"]
-----------------------------------------------------------------
-lttng enable-event --userspace hello:world
-lttng enable-event --userspace hello:world --loglevel=TRACE_INFO
-----------------------------------------------------------------
+----
+$ lttng enable-event --userspace hello:world
+$ lttng enable-event --userspace hello:world --loglevel=TRACE_INFO
+----
Here, two event rules are created. The first one has a single condition:
the tracepoint name must match `hello:world`. The second one has two
(option:--probe or option:--function option's argument) which must
match event source's equivalent.
+
-Wildcard using the `*` character are supported _at the end_ of
-tracepoint and system call names.
+You can use `*` characters at any place in the tracepoint or system
+call name as wildcards to match zero or more characters. To use a
+literal `*` character, use :escwc:.
* Filter expression (option:--filter option) executed against the
dynamic values of event fields at execution time that must evaluate
* Tracepoint name ('EVENT' with option:--tracepoint option) which must
match event source's equivalent.
+
-Wildcard using the `*` character are supported _at the end_ of
-tracepoint names. When creating an event rule with a tracepoint name
-containing a wildcard, specific tracepoint names can be excluded from
-the match using the option:--exclude option.
+You can use `*` characters at any place in the tracepoint name as
+wildcards to match zero or more characters. To use a literal `*`
+character, use :escwc:. When you create an event rule with a tracepoint
+name containing a wildcard, you can exclude specific tracepoint names
+from the match with the option:--exclude option.
* Filter expression (option:--filter option) executed against the
dynamic values of event fields at execution time that must evaluate
[[filter-syntax]]
Filter expression syntax
~~~~~~~~~~~~~~~~~~~~~~~~
-Filter expressions can be specified with the option:--filter option
-when creating a new event rule. If the filter expression evaluates
-to true when executed against the dynamic values of an event's fields
-when tracing, the filtering condition passes.
+A filter expression can be specified with the option:--filter option
+when creating a new event rule. If the filter expression evaluates to
+true when executed against the dynamic values of an event's fields when
+tracing, the filtering condition passes.
NOTE: Make sure to **single-quote** the filter expression when running
the command from a shell, as filter expressions typically include
The precedence table of the operators above is the same as the one of
the C language. Parentheses are supported to bypass this.
-The dynamic value of an event field is read by using its name as
-a C identifier.
+The dynamic value of an event field is read by using its name as a C
+identifier.
The dynamic value of a statically-known context field is read by
prefixing its name with `$ctx.`. Statically-known context fields are
context fields added to channels without the `$app.` prefix using the
-man:lttng-add-context(1) command.
+man:lttng-add-context(1) command. `$ctx.cpu_id` is also available as the
+ID of the CPU which emits the event.
The dynamic value of an application-specific context field is read by
prefixing its name with `$app.` (follows the format used to add such a
expression evaluates to false (the event is discarded).
C integer and floating point number constants are supported, as well as
-literal strings between double quotes (`"`). Literal strings can contain
-a wildcard character (`*`) at the end to match more than one string.
-This wildcard can be escaped using :escwc:.
+literal strings between double quotes (`"`). You can use `*` characters
+at any place in a literal string as wildcards to match zero or more
+characters. To use a literal `*` character, use :escwc:.
LTTng-UST enumeration fields can be compared to integer values (fields
or constants).
$app.my_provider:my_context == 17.34e9 || some_enum >= 14
---------------------------------------------------------
+---------------------------------------
+$ctx.cpu_id == 2 && filename != "*.log"
+---------------------------------------
+
[[log-levels]]
Log levels
Target
~~~~~~
-option:-c, option:--channel='CHANNEL'::
+option:-c 'CHANNEL', option:--channel='CHANNEL'::
Create or enable event rules in the channel named 'CHANNEL' instead
of the default channel name `channel0`.
-option:-s, option:--session='SESSION'::
+option:-s 'SESSION', option:--session='SESSION'::
Create or enable event rules in the tracing session named 'SESSION'
instead of the current tracing session.
Filtering and exclusion
~~~~~~~~~~~~~~~~~~~~~~~
-option:-x, option:--exclude='EVENT'[,'EVENT']...::
+option:-x 'EVENT'[,'EVENT']..., option:--exclude='EVENT'[,'EVENT']...::
Exclude events named 'EVENT' from the event rule. This option
- can be used when the command's 'EVENT' argument contains a wildcard
- (`*`) to exclude specific names. Only available with application
- domains.
+ can be used when the command's 'EVENT' argument contains at least
+ one wildcard star (`*`) to exclude specific names. 'EVENT' can also
+ contain wildcard stars. To use a
+ literal `,` character, use :esccomma:.
+ Only available with the option:--userspace domain.
-option:-f, option:--filter='EXPR'::
+option:-f 'EXPR', option:--filter='EXPR'::
Add filter expression condition to the event rule. Expression 'EXPR'
must evaluate to true when executed against the dynamic values of
event fields. See the <<filter-syntax,Filter expression syntax>>
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