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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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POSIX_T...XT_EVENT(3P) POSIX Programmer's Manual POSIX_T...XT_EVENT(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
posix_trace_getnext_event, posix_trace_timedgetnext_event,
posix_trace_trygetnext_event — retrieve a trace event (TRACING)
#include <sys/types.h>
#include <trace.h>
int posix_trace_getnext_event(trace_id_t trid,
struct posix_trace_event_info *restrict event,
void *restrict data, size_t num_bytes,
size_t *restrict data_len, int *restrict unavailable);
int posix_trace_timedgetnext_event(trace_id_t trid,
struct posix_trace_event_info *restrict event,
void *restrict data, size_t num_bytes,
size_t *restrict data_len, int *restrict unavailable,
const struct timespec *restrict abstime);
int posix_trace_trygetnext_event(trace_id_t trid,
struct posix_trace_event_info *restrict event,
void *restrict data, size_t num_bytes,
size_t *restrict data_len, int *restrict unavailable);
The posix_trace_getnext_event() function shall report a recorded
trace event either from an active trace stream without log or a
pre-recorded trace stream identified by the trid argument. The
posix_trace_trygetnext_event() function shall report a recorded
trace event from an active trace stream without log identified by
the trid argument.
The trace event information associated with the recorded trace
event shall be copied by the function into the structure pointed
to by the argument event and the data associated with the trace
event shall be copied into the buffer pointed to by the data
argument.
The posix_trace_getnext_event() function shall block if the trid
argument identifies an active trace stream and there is currently
no trace event ready to be retrieved. When returning, if a
recorded trace event was reported, the variable pointed to by the
unavailable argument shall be set to zero. Otherwise, the variable
pointed to by the unavailable argument shall be set to a value
different from zero.
The posix_trace_timedgetnext_event() function shall attempt to get
another trace event from an active trace stream without log, as in
the posix_trace_getnext_event() function. However, if no trace
event is available from the trace stream, the implied wait shall
be terminated when the timeout specified by the argument abstime
expires, and the function shall return the error [ETIMEDOUT].
The timeout shall expire when the absolute time specified by
abstime passes, as measured by the clock upon which timeouts are
based (that is, when the value of that clock equals or exceeds
abstime), or if the absolute time specified by abstime has already
passed at the time of the call.
The timeout shall be based on the CLOCK_REALTIME clock. The
resolution of the timeout shall be the resolution of the clock on
which it is based. The timespec data type is defined in the
<time.h> header.
Under no circumstance shall the function fail with a timeout if a
trace event is immediately available from the trace stream. The
validity of the abstime argument need not be checked if a trace
event is immediately available from the trace stream.
The behavior of this function for a pre-recorded trace stream is
unspecified.
The posix_trace_trygetnext_event() function shall not block. This
function shall return an error if the trid argument identifies a
pre-recorded trace stream. If a recorded trace event was
reported, the variable pointed to by the unavailable argument
shall be set to zero. Otherwise, if no trace event was reported,
the variable pointed to by the unavailable argument shall be set
to a value different from zero.
The argument num_bytes shall be the size of the buffer pointed to
by the data argument. The argument data_len reports to the
application the length in bytes of the data record just
transferred. If num_bytes is greater than or equal to the size of
the data associated with the trace event pointed to by the event
argument, all the recorded data shall be transferred. In this
case, the truncation-status member of the trace event structure
shall be either POSIX_TRACE_NOT_TRUNCATED, if the trace event data
was recorded without truncation while tracing, or
POSIX_TRACE_TRUNCATED_RECORD, if the trace event data was
truncated when it was recorded. If the num_bytes argument is less
than the length of recorded trace event data, the data transferred
shall be truncated to a length of num_bytes, the value stored in
the variable pointed to by data_len shall be equal to num_bytes,
and the truncation-status member of the event structure argument
shall be set to POSIX_TRACE_TRUNCATED_READ (see the
posix_trace_event_info structure defined in <trace.h>).
The report of a trace event shall be sequential starting from the
oldest recorded trace event. Trace events shall be reported in the
order in which they were generated, up to an implementation-
defined time resolution that causes the ordering of trace events
occurring very close to each other to be unknown. Once reported, a
trace event cannot be reported again from an active trace stream.
Once a trace event is reported from an active trace stream without
log, the trace stream shall make the resources associated with
that trace event available to record future generated trace
events.
Upon successful completion, these functions shall return a value
of zero. Otherwise, they shall return the corresponding error
number.
If successful, these functions store:
* The recorded trace event in the object pointed to by event
* The trace event information associated with the recorded trace
event in the object pointed to by data
* The length of this trace event information in the object
pointed to by data_len
* The value of zero in the object pointed to by unavailable
These functions shall fail if:
EINVAL The trace stream identifier argument trid is invalid.
The posix_trace_getnext_event() and
posix_trace_timedgetnext_event() functions shall fail if:
EINTR The operation was interrupted by a signal, and so the call
had no effect.
The posix_trace_trygetnext_event() function shall fail if:
EINVAL The trace stream identifier argument trid does not
correspond to an active trace stream.
The posix_trace_timedgetnext_event() function shall fail if:
EINVAL There is no trace event immediately available from the
trace stream, and the timeout argument is invalid.
ETIMEDOUT
No trace event was available from the trace stream before
the specified timeout timeout expired.
The following sections are informative.
None.
None.
None.
These functions may be removed in a future version.
posix_trace_close(3p), posix_trace_create(3p)
The Base Definitions volume of POSIX.1‐2017, sys_types.h(0p),
trace.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 POSIX_T...XT_EVENT(3P)
Pages that refer to this page: trace.h(0p), posix_trace_attr_getinherited(3p), posix_trace_close(3p), posix_trace_create(3p), posix_trace_eventid_equal(3p), posix_trace_eventtypelist_getnext_id(3p), posix_trace_timedgetnext_event(3p), posix_trace_trygetnext_event(3p)
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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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