--- name: "tep_filter_alloc" section: "3" platform: "linux" package: "libtraceevent" version: "1:1.9.1-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/tep_filter_alloc" --- # tep\_filter\_alloc(3) Event filter related APIs. ## NAME tep\_filter\_alloc, tep\_filter\_free, tep\_filter\_reset, tep\_filter\_make\_string, tep\_filter\_copy, tep\_filter\_compare, tep\_filter\_match, tep\_event\_filtered, tep\_filter\_remove\_event, tep\_filter\_strerror, tep\_filter\_add\_filter\_str - Event filter related APIs. ## SYNOPSIS ``` #include struct tep_event_filter *tep_filter_alloc(struct tep_handle *tep); void tep_filter_free(struct tep_event_filter *filter); void tep_filter_reset(struct tep_event_filter *filter); enum tep_errno tep_filter_add_filter_str(struct tep_event_filter *filter, const char *filter_str); int tep_event_filtered(struct tep_event_filter *filter, int event_id); int tep_filter_remove_event(struct tep_event_filter *filter, int event_id); enum tep_errno tep_filter_match(struct tep_event_filter *filter, struct tep_record *record); int tep_filter_copy(struct tep_event_filter *dest, struct tep_event_filter *source); int tep_filter_compare(struct tep_event_filter *filter1, struct tep_event_filter *filter2); char *tep_filter_make_string(struct tep_event_filter *filter, int event_id); int tep_filter_strerror(struct tep_event_filter *filter, enum tep_errno err, char *buf, size_t buflen); ``` ## DESCRIPTION Filters can be attached to traced events. They can be used to filter out various events when outputting them. Each event can be filtered based on its parameters, described in the event’s format file. This set of functions can be used to create, delete, modify and attach event filters. The **tep\_filter\_alloc()** function creates a new event filter. The *tep* argument is the trace event parser context. The **tep\_filter\_free()** function frees an event filter and all resources that it had used. The **tep\_filter\_reset()** function removes all rules from an event filter and resets it. The **tep\_filter\_add\_filter\_str()** function adds a new rule to the *filter*. The *filter\_str* argument is the filter string, that contains the rule. The **tep\_event\_filtered()** function checks if the event with *event\_id* has *filter*. The **tep\_filter\_remove\_event()** function removes a *filter* for an event with *event\_id*. The **tep\_filter\_match()** function tests if a *record* matches given *filter*. The **tep\_filter\_copy()** function copies a *source* filter into a *dest* filter. The **tep\_filter\_compare()** function compares two filers - *filter1* and *filter2*. The **tep\_filter\_make\_string()** function constructs a string, displaying the *filter* contents for given *event\_id*. The **tep\_filter\_strerror()** function copies the *filter* error buffer into the given *buf* with the size *buflen*. If the error buffer is empty, in the *buf* is copied a string, describing the error *err*. ## RETURN VALUE The **tep\_filter\_alloc()** function returns a pointer to the newly created event filter, or NULL in case of an error. The **tep\_filter\_add\_filter\_str()** function returns 0 if the rule was successfully added or a negative error code. Use **tep\_filter\_strerror()** to see actual error message in case of an error. The **tep\_event\_filtered()** function returns 1 if the filter is found for given event, or 0 otherwise. The **tep\_filter\_remove\_event()** function returns 1 if the vent was removed, or 0 if the event was not found. The **tep\_filter\_match()** function returns *tep\_errno*, according to the result: ``` TEP_ERRNO__FILTER_MATCH - filter found for event, the record matches. TEP_ERRNO__FILTER_MISS - filter found for event, the record does not match. TEP_ERRNO__FILTER_NOT_FOUND - no filter found for record’s event. TEP_ERRNO__NO_FILTER - no rules in the filter. ``` or any other *tep\_errno*, if an error occurred during the test. The **tep\_filter\_copy()** function returns 0 on success or -1 if not all rules were copied. The **tep\_filter\_compare()** function returns 1 if the two filters hold the same content, or 0 if they do not. The **tep\_filter\_make\_string()** function returns a string, which must be freed with free(), or NULL in case of an error. The **tep\_filter\_strerror()** function returns 0 if message was filled successfully, or -1 in case of an error. ## EXAMPLE ``` #include ... struct tep_handle *tep = tep_alloc(); ... char errstr[200]; int ret; struct tep_event_filter *filter = tep_filter_alloc(tep); struct tep_event_filter *filter1 = tep_filter_alloc(tep); ret = tep_filter_add_filter_str(filter, "sched/sched_wakeup:target_cpu==1"); if(ret < 0) { tep_filter_strerror(filter, ret, errstr, sizeof(errstr)); /* Failed to add a new rule to the filter, the error string is in errstr */ } if (tep_filter_copy(filter1, filter) != 0) { /* Failed to copy filter in filter1 */ } ... if (tep_filter_compare(filter, filter1) != 1) { /* Both filters are different */ } ... void process_record(struct tep_handle *tep, struct tep_record *record) { struct tep_event *event; char *fstring; event = tep_find_event_by_record(tep, record); if (tep_event_filtered(filter, event->id) == 1) { /* The event has filter */ fstring = tep_filter_make_string(filter, event->id); if (fstring != NULL) { /* The filter for the event is in fstring */ free(fstring); } } switch (tep_filter_match(filter, record)) { case TEP_ERRNO__FILTER_MATCH: /* The filter matches the record */ break; case TEP_ERRNO__FILTER_MISS: /* The filter does not match the record */ break; case TEP_ERRNO__FILTER_NOT_FOUND: /* No filter found for record's event */ break; case TEP_ERRNO__NO_FILTER: /* There are no rules in the filter */ break default: /* An error occurred during the test */ break; } if (tep_filter_remove_event(filter, event->id) == 1) { /* The event was removed from the filter */ } } ... tep_filter_reset(filter); ... tep_filter_free(filter); tep_filter_free(filter1); ... ``` ## FILES ``` event-parse.h Header file to include in order to have access to the library APIs. -ltraceevent Linker switch to add when building a program that uses the library. ``` ## SEE ALSO [**libtraceevent**(3)](/libtraceevent/3.md), [**trace-cmd**(1)](/trace-cmd/1.md) ## AUTHOR ``` Steven Rostedt , author of libtraceevent. Tzvetomir Stoyanov , author of this man page. ``` ## REPORTING BUGS Report bugs to \<**linux-trace-devel@vger.kernel.org**\[3\]\> ## LICENSE libtraceevent is Free Software licensed under the GNU LGPL 2.1 ## RESOURCES **https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/** ## NOTES - 1\. rostedt@goodmis.org mailto:rostedt@goodmis.org - 2\. tz.stoyanov@gmail.com mailto:tz.stoyanov@gmail.com - 3\. linux-trace-devel@vger.kernel.org mailto:linux-trace-devel@vger.kernel.org