1LIBTRACECMD(3) libtracefs Manual LIBTRACECMD(3)
2
6 tracecmd_read_cpu_first, tracecmd_read_data, tracecmd_read_at,
7 tracecmd_free_record, tracecmd_get_tep - Read recorded events from a
8 trace file.
9
11 #include <trace-cmd.h>
12 struct tep_record *tracecmd_read_cpu_first(struct tracecmd_input *handle, int cpu);
14 struct tep_record *tracecmd_read_data(struct tracecmd_input *handle, int cpu);
15 struct tep_record *tracecmd_read_at(struct tracecmd_input *handle, unsigned long long offset, int *cpu);
16 void tracecmd_free_record(struct tep_record *record);
17 struct tep_handle *tracecmd_get_tep(struct tracecmd_input *handle);
18
20 This set of APIs can be used to read tracing data from a trace file
21 opened with tracecmd_open()(3), tracecmd_open_fd()(3) or
22 tracecmd_open_head()(3).
23 The tracecmd_read_cpu_first() function reads the first trace record for
25 a given cpu from a trace file associated with handle. The returned
26 record must be freed with tracecmd_free_record().
27 The tracecmd_read_data() function reads the next trace record for a
29 given cpu from a trace file associated with handle and increments the
30 read location pointer, so that the next call to tracecmd_read_data()
31 will not read the same record again. The returned record must be freed
32 with tracecmd_free_record().
33 The tracecmd_read_at() function reads a trace record from a specific
35 offset within the file associated with handle. The CPU on which the
36 recorded event occurred is stored in the cpu. The function does not
37 change the current read location pointer. The returned record must be
38 freed with tracecmd_free_record().
39 The tracecmd_free_record() function frees a record returned by any of
41 the tracecmd_read_ APIs.
42 The tracecmd_get_tep() function returns a tep context for a given
44 handle.
45
47 The tracecmd_read_cpu_first(), tracecmd_read_data() and
48 tracecmd_read_at() functions return a pointer to struct tep_record or
49 NULL in case of an error.The returned record must be freed with
50 tracecmd_free_record().
51 The tracecmd_get_tep() function returns a pointer to tep context or
53 NULL if there is no tep context for the given handle. The returned tep
54 pointer must not be freed.
55
57 #include <trace-cmd.h>
58 ...
59 struct tracecmd_input *handle = tracecmd_open("trace.dat");
60 if (!handle) {
61 /* Failed to open trace.dat file */
62 }
63 ...
64 unsigned long long offset = 0;
65 struct tep_record *rec;
66 int cpu = 0;
67 rec = tracecmd_read_cpu_first(handle, cpu);
68 while (rec) {
69 ...
70 if ( /* some interesting record noticed */) {
71 /* store the offset of the interesting record */
72 offset = rec->offset;
73 }
74 ...
75 tracecmd_free_record(rec);
76 rec = tracecmd_read_data(handle, cpu);
77 }
78 ...
79 if (offset) {
80 rec = tracecmd_read_at(handle, offset, &cpu);
81 if (rec) {
82 /* Got record at offset on cpu */
83 ...
84 tracecmd_free_record(rec);
85 }
86 }
87 ...
89 tracecmd_close(hadle);
90
92 trace-cmd.h
93 Header file to include in order to have access to the library APIs.
94 -ltracecmd
95 Linker switch to add when building a program that uses the library.
96
98 libtracefs(3), libtraceevent(3), trace-cmd(1) trace-cmd.dat(5)
99
101 Steven Rostedt <rostedt@goodmis.org[1]>
102 Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>
103
105 Report bugs to <linux-trace-devel@vger.kernel.org[3]>
106
108 libtracecmd is Free Software licensed under the GNU LGPL 2.1
109
111 https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/
112
114 Copyright (C) 2020 VMware, Inc. Free use of this software is granted
115 under the terms of the GNU Public License (GPL).
116
118 1. rostedt@goodmis.org
119 mailto:rostedt@goodmis.org
120 2. tz.stoyanov@gmail.com
122 mailto:tz.stoyanov@gmail.com
123 3. linux-trace-devel@vger.kernel.org
125 mailto:linux-trace-devel@vger.kernel.org
126libtracefs 04/15/2022 LIBTRACECMD(3)