\-\-filter 'expression'
Set a filter on a newly enabled event. Filter expression on event
- fields, event recording depends on evaluation. Only specify on first
- activation of a given event within a session. Filter only allowed when
- enabling events within a session before tracing is started. If the
- filter fails to link with the event within the traced domain, the event
- will be discarded. Currently, filter is only implemented for the
- user-space tracer.
+ fields and context. Event recording depends on evaluation. Only
+ specify on first activation of a given event within a session.
+ Filter only allowed when enabling events within a session before
+ tracing is started. If the filter fails to link with the event
+ within the traced domain, the event will be discarded.
+ Currently, filter is only implemented for the user-space tracer.
Expression examples:
Wildcards are allowed at the end of strings:
'seqfield1 == "te*"'
In string literals, the escape character is a '\\'. Use '\\*' for
- the '*' character, and '\\\\' for the '\\' character.
+ the '*' character, and '\\\\' for the '\\' character. Wildcard
+ match any sequence of characters, including an empty sub-string
+ (match 0 or more characters).
+
+ Context information can be used for filtering. The examples
+ below show usage of context filtering on process name (with a
+ wildcard), process ID range, and unique thread ID for filtering.
+ The process and thread ID of running applications can be found
+ under columns "PID" and "LWP" of the "ps -eLf" command.
+
+ '$ctx.procname == "demo*"'
+ '$ctx.vpid >= 4433 && $ctx.vpid < 4455'
+ '$ctx.vtid == 1234'
.fi
.IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"