1POSIX_TRACE_GETNEXT_EVENT(3PP)OSIX Programmer's ManuPaOlSIX_TRACE_GETNEXT_EVENT(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 posix_trace_getnext_event, posix_trace_timedgetnext_event,
13 posix_trace_trygetnext_event — retrieve a trace event (TRACING)
14
16 #include <sys/types.h>
17 #include <trace.h>
18 int posix_trace_getnext_event(trace_id_t trid,
20 struct posix_trace_event_info *restrict event,
21 void *restrict data, size_t num_bytes,
22 size_t *restrict data_len, int *restrict unavailable);
23 int posix_trace_timedgetnext_event(trace_id_t trid,
24 struct posix_trace_event_info *restrict event,
25 void *restrict data, size_t num_bytes,
26 size_t *restrict data_len, int *restrict unavailable,
27 const struct timespec *restrict abstime);
28 int posix_trace_trygetnext_event(trace_id_t trid,
29 struct posix_trace_event_info *restrict event,
30 void *restrict data, size_t num_bytes,
31 size_t *restrict data_len, int *restrict unavailable);
32
34 The posix_trace_getnext_event() function shall report a recorded trace
35 event either from an active trace stream without log or a pre-recorded
36 trace stream identified by the trid argument. The posix_trace_tryget‐
37 next_event() function shall report a recorded trace event from an
38 active trace stream without log identified by the trid argument.
39 The trace event information associated with the recorded trace event
41 shall be copied by the function into the structure pointed to by the
42 argument event and the data associated with the trace event shall be
43 copied into the buffer pointed to by the data argument.
44 The posix_trace_getnext_event() function shall block if the trid argu‐
46 ment identifies an active trace stream and there is currently no trace
47 event ready to be retrieved. When returning, if a recorded trace event
48 was reported, the variable pointed to by the unavailable argument shall
49 be set to zero. Otherwise, the variable pointed to by the unavailable
50 argument shall be set to a value different from zero.
51 The posix_trace_timedgetnext_event() function shall attempt to get
53 another trace event from an active trace stream without log, as in the
54 posix_trace_getnext_event() function. However, if no trace event is
55 available from the trace stream, the implied wait shall be terminated
56 when the timeout specified by the argument abstime expires, and the
57 function shall return the error [ETIMEDOUT].
58 The timeout shall expire when the absolute time specified by abstime
60 passes, as measured by the clock upon which timeouts are based (that
61 is, when the value of that clock equals or exceeds abstime), or if the
62 absolute time specified by abstime has already passed at the time of
63 the call.
64 The timeout shall be based on the CLOCK_REALTIME clock. The resolution
66 of the timeout shall be the resolution of the clock on which it is
67 based. The timespec data type is defined in the <time.h> header.
68 Under no circumstance shall the function fail with a timeout if a trace
70 event is immediately available from the trace stream. The validity of
71 the abstime argument need not be checked if a trace event is immedi‐
72 ately available from the trace stream.
73 The behavior of this function for a pre-recorded trace stream is
75 unspecified.
76 The posix_trace_trygetnext_event() function shall not block. This
78 function shall return an error if the trid argument identifies a pre-
79 recorded trace stream. If a recorded trace event was reported, the
80 variable pointed to by the unavailable argument shall be set to zero.
81 Otherwise, if no trace event was reported, the variable pointed to by
82 the unavailable argument shall be set to a value different from zero.
83 The argument num_bytes shall be the size of the buffer pointed to by
85 the data argument. The argument data_len reports to the application the
86 length in bytes of the data record just transferred. If num_bytes is
87 greater than or equal to the size of the data associated with the trace
88 event pointed to by the event argument, all the recorded data shall be
89 transferred. In this case, the truncation-status member of the trace
90 event structure shall be either POSIX_TRACE_NOT_TRUNCATED, if the trace
91 event data was recorded without truncation while tracing, or
92 POSIX_TRACE_TRUNCATED_RECORD, if the trace event data was truncated
93 when it was recorded. If the num_bytes argument is less than the length
94 of recorded trace event data, the data transferred shall be truncated
95 to a length of num_bytes, the value stored in the variable pointed to
96 by data_len shall be equal to num_bytes, and the truncation-status mem‐
97 ber of the event structure argument shall be set to POSIX_TRACE_TRUN‐
98 CATED_READ (see the posix_trace_event_info structure defined in
99 <trace.h>).
100 The report of a trace event shall be sequential starting from the old‐
102 est recorded trace event. Trace events shall be reported in the order
103 in which they were generated, up to an implementation-defined time res‐
104 olution that causes the ordering of trace events occurring very close
105 to each other to be unknown. Once reported, a trace event cannot be
106 reported again from an active trace stream. Once a trace event is
107 reported from an active trace stream without log, the trace stream
108 shall make the resources associated with that trace event available to
109 record future generated trace events.
110
112 Upon successful completion, these functions shall return a value of
113 zero. Otherwise, they shall return the corresponding error number.
114 If successful, these functions store:
116 * The recorded trace event in the object pointed to by event
118 * The trace event information associated with the recorded trace
120 event in the object pointed to by data
121 * The length of this trace event information in the object pointed to
123 by data_len
124 * The value of zero in the object pointed to by unavailable
126
128 These functions shall fail if:
129 EINVAL The trace stream identifier argument trid is invalid.
131 The posix_trace_getnext_event() and posix_trace_timedgetnext_event()
133 functions shall fail if:
134 EINTR The operation was interrupted by a signal, and so the call had
136 no effect.
137 The posix_trace_trygetnext_event() function shall fail if:
139 EINVAL The trace stream identifier argument trid does not correspond to
141 an active trace stream.
142 The posix_trace_timedgetnext_event() function shall fail if:
144 EINVAL There is no trace event immediately available from the trace
146 stream, and the timeout argument is invalid.
147 ETIMEDOUT
149 No trace event was available from the trace stream before the
150 specified timeout timeout expired.
151 The following sections are informative.
153
155 None.
156
158 None.
159
161 None.
162
164 These functions may be removed in a future version.
165
167 posix_trace_close(), posix_trace_create()
168 The Base Definitions volume of POSIX.1‐2017, <sys_types.h>, <trace.h>
170
172 Portions of this text are reprinted and reproduced in electronic form
173 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
174 table Operating System Interface (POSIX), The Open Group Base Specifi‐
175 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
176 Electrical and Electronics Engineers, Inc and The Open Group. In the
177 event of any discrepancy between this version and the original IEEE and
178 The Open Group Standard, the original IEEE and The Open Group Standard
179 is the referee document. The original Standard can be obtained online
180 at http://www.opengroup.org/unix/online.html .
181 Any typographical or formatting errors that appear in this page are
183 most likely to have been introduced during the conversion of the source
184 files to man page format. To report such errors, see https://www.ker‐
185 nel.org/doc/man-pages/reporting_bugs.html .
186IEEE/The Open Group 2017 POSIX_TRACE_GETNEXT_EVENT(3P)