--- name: "tracefs_local_events" section: "3" platform: "linux" package: "libtracefs" version: "1.8.4-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/tracefs_local_events" --- # tracefs\_local\_events(3) Initialize a tep handler with trace events from the local system. ## NAME tracefs\_local\_events, tracefs\_local\_events\_system, tracefs\_fill\_local\_events, tracefs\_load\_cmdlines, tracefs\_load\_headers - Initialize a tep handler with trace events from the local system. ## SYNOPSIS ``` #include struct tep_handle *tracefs_local_events(const char *tracing_dir); struct tep_handle *tracefs_local_events_system(const char *tracing_dir, const char * const *sys_names); int tracefs_fill_local_events(const char *tracing_dir, struct tep_handle *tep, int *parsing_failures); int tracefs_load_cmdlines(const char *tracing_dir, struct tep_handle *tep); int tracefs_load_headers(const char *tracing_dir, struct tep_handle *tep); ``` ## DESCRIPTION Functions for initializing a tep handler with trace events from the local system. The **tracefs\_local\_events()** function allocates a new *tep* handler and initializes it with events from all trace systems, located in the given *tracing\_dir* directory. This could be NULL or the location of the tracefs mount point for the trace systems of the local machine, or it may be a path to a copy of the tracefs directory from another machine. The **tracefs\_local\_events\_system()** function allocates a new *tep* handler and initializes it with events from specified trace systems *sys\_names*, located in the given *tracing\_dir* directory. This could be NULL or the location of the tracefs mount point for the trace systems of the local machine, or it may be a path to a copy of the tracefs directory from another machine. The *sys\_names* argument is an array of trace system names, that will be used for *tep* handler initialization. The last element in that array must be a NULL pointer. The **tracefs\_fill\_local\_events()** function initializes already allocated *tep* handler with events from all trace systems, located in the given *tracing\_dir* directory. This could be NULL or the location of the tracefs mount point for the trace systems of the local machine, or it may be a path to a copy of the tracefs directory from another machine. The *tep* argument must be a pointer to already allocated tep handler, that is going to be initialized. The *parsing\_failures* argument could be NULL or a pointer to an integer, where the number of failures while parsing the event files are returned. The above functions will also load the mappings between pids and the process command line names. In some cases the *tep* handle is created with one of the above before tracing begins. As the mappings get updated during the trace, there may be a need to read the mappings again after the trace. The **tracefs\_load\_cmdlines()** does just that. The *tracing\_dir* is the directory of the mount point to load from, or NULL to use the mount point of the tracefs file system. The **tracefs\_load\_headers()** will reade the "header\_page" of the events directory that will update the *tep* handle with information on how to parse the tracing ring buffer sub-buffer. ## RETURN VALUE The **tracefs\_local\_events()** and **tracefs\_local\_events\_system()** functions return pointer to allocated and initialized *tep* handler, or NULL in case of an error. The returned *tep* handler must be freed with [**tep\_free**(3)](/tep_free/3.md). The **tracefs\_fill\_local\_events()** function returns -1 in case of an error or 0 otherwise. The **tracefs\_load\_cmdlines()** function returns -1 in case of an error, or 0 otherwise. ## EXAMPLE ``` #include struct tep_handle *tep; ... tep = tracefs_local_events(NULL); if (!tep) { /* Failed to initialise tep handler with local events from top instance */ ... } ... tep_free(tep); ... const char *systems[] = {"ftrace", "irq", NULL}; tep = tracefs_local_events_system(NULL, systems); if (!tep) { /* Failed to initialise tep handler with local events from * ftrace and irq systems in top instance. */ ... } ... tep_free(tep); ... int parsing_failures; tep = tep_alloc(); if (!tep) { /* Failed to allocate a tep handler */ ... } if (tracefs_fill_local_events(NULL, tep, &parsing_failures) < 0) { /* Failed to initialise tep handler with local events from top instance */ } tracefs_load_cmdlines(NULL, tep); ... tep_free(tep); ``` ## FILES ``` tracefs.h Header file to include in order to have access to the library APIs. -ltracefs Linker switch to add when building a program that uses the library. ``` ## SEE ALSO [**libtracefs**(3)](/libtracefs/3.md), [**libtraceevent**(3)](/libtraceevent/3.md), [**trace-cmd**(1)](/trace-cmd/1.md) ## AUTHOR ``` Steven Rostedt Tzvetomir Stoyanov ``` ## REPORTING BUGS Report bugs to \<**linux-trace-devel@vger.kernel.org**\[3\]\> ## LICENSE libtracefs is Free Software licensed under the GNU LGPL 2.1 ## RESOURCES **https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/** ## COPYING Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL). ## 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