Create or enable Linux kernel event rules:
[verse]
-*lttng* ['GENERAL OPTIONS'] *enable-event* option:--kernel
+*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *enable-event* option:--kernel
[option:--probe='SOURCE' | option:--function='SOURCE' | option:--syscall]
[option:--filter='EXPR'] [option:--session='SESSION']
[option:--channel='CHANNEL'] 'EVENT'[,'EVENT']...
Create or enable an "all" Linux kernel event rule:
[verse]
-*lttng* ['GENERAL OPTIONS'] *enable-event* option:--kernel option:--all [option:--syscall]
+*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *enable-event* option:--kernel option:--all [option:--syscall]
[option:--filter='EXPR'] [option:--session='SESSION'] [option:--channel='CHANNEL']
Create or enable application event rules:
[verse]
-*lttng* ['GENERAL OPTIONS'] *enable-event*
+*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *enable-event*
(option:--userspace | option:--jul | option:--log4j | option:--python)
[option:--filter='EXPR'] [option:--exclude='EVENT'[,'EVENT']...]
[option:--loglevel='LOGLEVEL' | option:--loglevel-only='LOGLEVEL']
that must be satisfied in order for an actual event to be emitted by
an LTTng tracer when the execution of an application or the Linux kernel
reaches an event source (tracepoint, system call, dynamic probe).
-Event sources can be listed with the linklttng:lttng-list(1) command.
+Event sources can be listed with the man:lttng-list(1) command.
-The linklttng:lttng-disable-event(1) command can be used to disable
+The man:lttng-disable-event(1) command can be used to disable
existing event rules.
Event rules are always assigned to a channel when they are created. If
from the current tracing session.
Events can be enabled while tracing is active
-(use linklttng:lttng-start(1) to make a tracing session active).
+(use man:lttng-start(1) to make a tracing session active).
Event source types
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
currently exist for the chosen tracing session, domain, and channel,
a new event rule is created. Otherwise, the existing event rule is
enabled if it is currently disabled
-(see linklttng:lttng-disable-event(1)).
+(see man:lttng-disable-event(1)).
The option:--all option can be used alongside the option:--tracepoint
or option:--syscall options. When this option is used, no 'EVENT'
[[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
-linklttng: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
-context field with the linklttng:lttng-add-context(1) command).
+context field with the man:lttng-add-context(1) command).
When a comparison includes a non existent event field, the whole filter
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 `\\*`.
+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).
NOTE: Although it is possible to filter the process ID of an event when
the `pid` context has been added to its channel using, for example,
`$ctx.pid == 2832`, it is recommended to use the PID tracker instead,
-which is much more efficient (see linklttng:lttng-track(1)).
+which is much more efficient (see man:lttng-track(1)).
Examples:
$app.my_provider:my_context == 17.34e9 || some_enum >= 14
---------------------------------------------------------
+---------------------------------------
+$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>>
SEE ALSO
--------
-linklttng:lttng-disable-event(1),
-linklttng:lttng(1)
+man:lttng-disable-event(1),
+man:lttng(1)
projects / lttng-tools.git / blobdiff