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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | COPYING | NOTES | COLOPHON |
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LIBTRACEFS(3) libtracefs Manual LIBTRACEFS(3)
tracefs_eprobe_alloc - Allocate new event probe (eprobe)
#include <tracefs.h>
struct tracefs_dynevent *
tracefs_eprobe_alloc(const char *system, const char *event,
const char *target_system, const char *target_event,
const char *fetchargs);
tracefs_eprobe_alloc() allocates a new eprobe context. The ebrobe
is not configured in the system. The new eprobe will be in the
system group (or eprobes if system is NULL) and have the name of
event. The eprobe will be attached to target_event, located in
target_system. The list of arguments, described in fetchargs, will
be fetched from target_event. The returned pointer to the event
probe must be freed with tracefs_dynevent_free().
The tracefs_eprobe_alloc() API returns a pointer to an allocated
tracefs_dynevent structure, describing the event probe. This
pointer must be freed by tracefs_dynevent_free(3). Note, this only
allocates a descriptor representing the eprobe. It does not modify
the running system. On error NULL is returned.
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <tracefs.h>
static struct tep_event *open_event;
static struct tep_format_field *file_field;
static int callback(struct tep_event *event, struct tep_record *record,
int cpu, void *data)
{
struct trace_seq seq;
trace_seq_init(&seq);
tep_print_event(event->tep, &seq, record, "%d-%s: ", TEP_PRINT_PID, TEP_PRINT_COMM);
if (event->id == open_event->id) {
trace_seq_puts(&seq, "open file='");
tep_print_field(&seq, record->data, file_field);
trace_seq_puts(&seq, "'\n");
}
trace_seq_terminate(&seq);
trace_seq_do_printf(&seq);
trace_seq_destroy(&seq);
return 0;
}
static pid_t run_exec(char **argv, char **env)
{
pid_t pid;
pid = fork();
if (pid)
return pid;
execve(argv[0], argv, env);
perror("exec");
exit(-1);
}
const char *myprobe = "my_eprobes";
int main (int argc, char **argv, char **env)
{
struct tracefs_dynevent *eprobe;
struct tracefs_instance *instance;
struct tep_handle *tep;
const char *sysnames[] = { myprobe, NULL };
pid_t pid;
if (argc < 2) {
printf("usage: %s command\n", argv[0]);
exit(-1);
}
instance = tracefs_instance_create("exec_open");
if (!instance) {
perror("creating instance");
exit(-1);
}
tracefs_dynevent_destroy_all(TRACEFS_DYNEVENT_EPROBE, true);
eprobe = tracefs_eprobe_alloc(myprobe, "sopen", "syscalls", "sys_enter_openat2",
"file=+0($filename):ustring");
if (!eprobe) {
perror("allocating event probe");
exit(-1);
}
if (tracefs_dynevent_create(eprobe)) {
perror("creating event probe");
exit(-1);
}
tep = tracefs_local_events_system(NULL, sysnames);
if (!tep) {
perror("reading events");
exit(-1);
}
open_event = tep_find_event_by_name(tep, myprobe, "sopen");
file_field = tep_find_field(open_event, "file");
tracefs_event_enable(instance, myprobe, "sopen");
pid = run_exec(&argv[1], env);
/* Let the child start to run */
sched_yield();
do {
tracefs_load_cmdlines(NULL, tep);
tracefs_iterate_raw_events(tep, instance, NULL, 0, callback, NULL);
} while (waitpid(pid, NULL, WNOHANG) != pid);
/* Will disable the events */
tracefs_dynevent_destroy(eprobe, true);
tracefs_dynevent_free(eprobe);
tracefs_instance_destroy(instance);
tep_free(tep);
return 0;
}
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.
libtracefs(3), libtraceevent(3), trace-cmd(1)
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
libtracefs is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
Copyright (C) 2021 VMware, Inc. Free use of this software is
granted under the terms of the GNU Public License (GPL).
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
This page is part of the libtracefs (Linux kernel trace file
system library) project. Information about the project can be
found at ⟨https://www.trace-cmd.org/⟩. If you have a bug report
for this manual page, see ⟨https://www.trace-cmd.org/⟩. This page
was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-06-02.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
libtracefs 1.7.0 12/22/2023 LIBTRACEFS(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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