PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

POSIX_TRACE_GETNEXT_EVENT(3P)IX Programmer's ManualX_TRACE_GETNEXT_EVENT(3P)

PROLOG         top

       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         top

       posix_trace_getnext_event, posix_trace_timedgetnext_event,
       posix_trace_trygetnext_event — retrieve a trace event (TRACING)

SYNOPSIS         top

       #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         top

       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.

RETURN VALUE         top

       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         top

       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         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       These functions may be removed in a future version.

SEE ALSO         top

       posix_trace_close(3p), posix_trace_create(3p)

       The Base Definitions volume of POSIX.1‐2008, sys_types.h(0p),
       trace.h(0p)

COPYRIGHT         top

       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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013       POSIX_TRACE_GETNEXT_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)