POSIX_TRACE_GETNEXT_EVENT(3POSIX Programmer's ManPOSIX_TRACE_GETNEXT_EVENT(3P)
PROLOG
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.
NAME
posix_trace_getnext_event, posix_trace_timedgetnext_event,
posix_trace_trygetnext_event -- retrieve a trace event (TRACING)
SYNOPSIS
#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);
DESCRIPTION
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_tryget-
next_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 argu-
ment 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 immedi-
ately 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 mem-
ber of the event structure argument shall be set to POSIX_TRACE_TRUN-
CATED_READ (see the posix_trace_event_info structure defined in
<trace.h>).
The report of a trace event shall be sequential starting from the old-
est recorded trace event. Trace events shall be reported in the order
in which they were generated, up to an implementation-defined time res-
olution 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.
RETURN VALUE
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
ERRORS
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.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
These functions may be removed in a future version.
SEE ALSO
posix_trace_close(), posix_trace_create()
The Base Definitions volume of POSIX.1-2008, <sys_types.h>, <trace.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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.ker-
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 POSIX_TRACE_GETNEXT_EVENT(3P)
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