LIBTRACECMD(3) libtracefs Manual LIBTRACECMD(3)
NAME
tracecmd_read_cpu_first, tracecmd_read_data, tracecmd_read_at,
tracecmd_free_record, tracecmd_get_tep - Read recorded events from a
trace file.
SYNOPSIS
#include <trace-cmd.h>
struct tep_record *tracecmd_read_cpu_first(struct tracecmd_input *handle, int cpu);
struct tep_record *tracecmd_read_data(struct tracecmd_input *handle, int cpu);
struct tep_record *tracecmd_read_at(struct tracecmd_input *handle, unsigned long long offset, int *cpu);
void tracecmd_free_record(struct tep_record *record);
struct tep_handle *tracecmd_get_tep(struct tracecmd_input *handle);
DESCRIPTION
This set of APIs can be used to read tracing data from a trace file
opened with tracecmd_open()(3), tracecmd_open_fd()(3) or
tracecmd_open_head()(3).
The tracecmd_read_cpu_first() function reads the first trace record for
a given cpu from a trace file associated with handle. The returned
record must be freed with tracecmd_free_record().
The tracecmd_read_data() function reads the next trace record for a
given cpu from a trace file associated with handle and increments the
read location pointer, so that the next call to tracecmd_read_data()
will not read the same record again. The returned record must be freed
with tracecmd_free_record().
The tracecmd_read_at() function reads a trace record from a specific
offset within the file associated with handle. The CPU on which the
recorded event occurred is stored in the cpu. The function does not
change the current read location pointer. The returned record must be
freed with tracecmd_free_record().
The tracecmd_free_record() function frees a record returned by any of
the tracecmd_read_ APIs.
The tracecmd_get_tep() function returns a tep context for a given
handle.
RETURN VALUE
The tracecmd_read_cpu_first(), tracecmd_read_data() and
tracecmd_read_at() functions return a pointer to struct tep_record or
NULL in case of an error.The returned record must be freed with
tracecmd_free_record().
The tracecmd_get_tep() function returns a pointer to tep context or
NULL if there is no tep context for the given handle. The returned tep
pointer must not be freed.
EXAMPLE
#include <trace-cmd.h>
...
struct tracecmd_input *handle = tracecmd_open("trace.dat");
if (!handle) {
/* Failed to open trace.dat file */
}
...
unsigned long long offset = 0;
struct tep_record *rec;
int cpu = 0;
rec = tracecmd_read_cpu_first(handle, cpu);
while (rec) {
...
if ( /* some interesting record noticed */) {
/* store the offset of the interesting record */
offset = rec->offset;
}
...
tracecmd_free_record(rec);
rec = tracecmd_read_data(handle, cpu);
}
...
if (offset) {
rec = tracecmd_read_at(handle, offset, &cpu);
if (rec) {
/* Got record at offset on cpu */
...
tracecmd_free_record(rec);
}
}
...
tracecmd_close(hadle);
FILES
trace-cmd.h
Header file to include in order to have access to the library APIs.
-ltracecmd
Linker switch to add when building a program that uses the library.
SEE ALSO
libtracefs(3), libtraceevent(3), trace-cmd(1) trace-cmd.dat(5)
AUTHOR
Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
REPORTING BUGS
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
LICENSE
libtracecmd is Free Software licensed under the GNU LGPL 2.1
RESOURCES
https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.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
libtracefs 04/08/2024 LIBTRACECMD(3)
Generated by dwww version 1.16 on Tue Dec 16 16:56:53 CET 2025.