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.TH POSIX_TRACE_EVENT "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"
.SH 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.

.SH NAME
posix_trace_event,
posix_trace_eventid_open
\(em trace functions for instrumenting application code
(\fBTRACING\fP)
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <trace.h>
.P
void posix_trace_event(trace_event_id_t \fIevent_id\fP,
    const void *restrict \fIdata_ptr\fP, size_t \fIdata_len\fP);
int posix_trace_eventid_open(const char *restrict \fIevent_name\fP,
    trace_event_id_t *restrict \fIevent_id\fP);
.fi
.SH DESCRIPTION
The
\fIposix_trace_event\fR()
function shall record the
.IR event_id
and the user data pointed to by
.IR data_ptr
in the trace stream into which the calling process is being traced and
in which
.IR event_id
is not filtered out. If the total size of the user trace event data
represented by
.IR data_len
is not greater than the declared maximum size for user trace event
data, then the
.IR 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
.IR truncation-status
attribute of the trace event recorded is POSIX_TRACE_TRUNCATED_RECORD.
.P
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
.IR event_id
is filtered out in the trace stream, the
\fIposix_trace_event\fR()
function shall have no effect.
.P
The
\fIposix_trace_eventid_open\fR()
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
.IR 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}.
.P
If the Trace Inherit option is not supported, the
\fIposix_trace_eventid_open\fR()
function shall associate the user trace event name pointed to by the
.IR 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
.IR 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
.IR "Table 2-7" ", " "Trace Option: User Trace Event")
user trace event shall be returned.
.P
If the Trace Inherit option is supported, the
\fIposix_trace_eventid_open\fR()
function shall associate the user trace event name pointed to by the
.IR 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
.IR 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 (\c
.IR "Table 2-7" ", " "Trace Option: User Trace Event")
user trace event shall be returned.
.TP 10
.BR 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.
.P
.P
If there is no trace stream created, the
\fIposix_trace_eventid_open\fR()
function shall store this information for future trace streams created
for this process.
.SH "RETURN VALUE"
No return value is defined for the
\fIposix_trace_event\fR()
function.
.P
Upon successful completion, the
\fIposix_trace_eventid_open\fR()
function shall return a value of zero. Otherwise, it shall return the
corresponding error number. The
\fIposix_trace_eventid_open\fR()
function stores the trace event type identifier value in the object
pointed to by
.IR event_id ,
if successful.
.SH ERRORS
The
\fIposix_trace_eventid_open\fR()
function shall fail if:
.TP
.BR ENAMETOOLONG
.br
The size of the name pointed to by the
.IR event_name
argument was longer than the implementation-defined value
{TRACE_EVENT_NAME_MAX}.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
The
\fIposix_trace_event\fR()
and
\fIposix_trace_eventid_open\fR()
functions may be removed in a future version.
.SH "SEE ALSO"
.IR "Table 2-7" ", " "Trace Option: User Trace Event",
.IR "\fIexec\fR\^",
.IR "\fIposix_trace_eventid_equal\fR\^(\|)",
.IR "\fIposix_trace_start\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2008,
.IR "\fB<sys_types.h>\fP",
.IR "\fB<trace.h>\fP"
.SH 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
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 .

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