POSIX_TRACE_EVENT(3P)                               POSIX Programmer's Manual                              POSIX_TRACE_EVENT(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       posix_trace_event, posix_trace_eventid_open - trace functions for instrumenting application code (TRACING)

SYNOPSIS
       #include <sys/types.h>
       #include <trace.h>

       void posix_trace_event(trace_event_id_t event_id,
              const void *restrictdata_ptr, size_t data_len);
       int posix_trace_eventid_open(const char *restrict event_name,
              trace_event_id_t *restrict event_id);


DESCRIPTION
       The  posix_trace_event()  function shall record the event_id and the user data pointed to by data_ptr in the trace stream
       into which the calling process is being traced and in which event_id is not filtered out. If the total size of  the  user
       trace  event  data  represented by data_len is not greater than the declared maximum size for user trace event data, then
       the truncation-status attribute of the trace event recorded is POSIX_TRACE_NOT_TRUNCATED. Otherwise, the user trace event
       data  is  truncated  to  this  declared  maximum  size and the truncation-status attribute of the trace event recorded is
       POSIX_TRACE_TRUNCATED_RECORD.

       If there is no trace stream created for the process or if the created trace stream is not running, or if the trace  event
       specified by event_id is filtered out in the trace stream, the posix_trace_event() function shall have no effect.

       The  posix_trace_eventid_open()  function  shall associate a user trace event name with a trace event type identifier for
       the calling process. The trace event name is the string pointed to by the argument event_name. It shall have a maximum of
       {TRACE_EVENT_NAME_MAX}  characters (which has the minimum value {_POSIX_TRACE_EVENT_NAME_MAX}).  The number of user trace
       event type identifiers that can be defined for any given process is limited by the maximum value  {TRACE_USER_EVENT_MAX},
       which has the minimum value {POSIX_TRACE_USER_EVENT_MAX}.

       If  the  Trace  Inherit  option  is not supported, the posix_trace_eventid_open() function shall associate the user trace
       event name pointed to by the event_name argument with a trace event  type  identifier  that  is  unique  for  the  traced
       process,  and  is returned in the variable pointed to by the event_id argument.  If the user trace event name has already
       been mapped for the traced process, then the previously assigned trace event type identifier shall be  returned.  If  the
       per-process  user  trace  event  name  limit  represented  by  {TRACE_USER_EVENT_MAX}  has  been reached, the pre-defined
       POSIX_TRACE_UNNAMED_USEREVENT (see Trace Option: User Trace Event ) user trace event shall be returned.

       If the Trace Inherit option is supported, the posix_trace_eventid_open() function shall associate the  user  trace  event
       name  pointed to by the event_name argument with a trace event type identifier that is unique for all the processes being
       traced in this same trace stream, and is returned in the variable pointed to by the event_id argument. If the user  trace
       event  name  has  already  been mapped for the traced processes, then the previously assigned trace event type identifier
       shall be returned. If the per-process user trace event name limit represented by {TRACE_USER_EVENT_MAX} has been reached,
       the pre-defined POSIX_TRACE_UNNAMED_USEREVENT ( Trace Option: User Trace Event ) user trace event shall be returned.

       Note:  The  above procedure, together with the fact that multiple processes can only be traced into the same trace stream
              by inheritance, ensure that all the processes that are traced into a trace stream have the same mapping  of  trace
              event names to trace event type identifiers.


       If  there  is  no  trace  stream created, the posix_trace_eventid_open() function shall store this information for future
       trace streams created for this process.

RETURN VALUE
       No return value is defined for the posix_trace_event() function.

       Upon successful completion, the posix_trace_eventid_open() function shall return a value of  zero.  Otherwise,  it  shall
       return  the  corresponding  error  number. The posix_trace_eventid_open() function stores the trace event type identifier
       value in the object pointed to by event_id, if successful.

ERRORS
       The posix_trace_eventid_open() function shall fail if:

       ENAMETOOLONG
              The size of the name pointed to by the event_name  argument  was  longer  than  the  implementation-defined  value
              {TRACE_EVENT_NAME_MAX}.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Trace  Option:  User  Trace  Event,  posix_trace_start(), posix_trace_trid_eventid_open(), the Base Definitions volume of
       IEEE Std 1003.1-2001, <sys/types.h>, <trace.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                         POSIX_TRACE_EVENT(3P)