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POSIX_TRACE_GETNEXT_EVENT
Section: POSIX Programmer's Manual (3P)
Updated: 2003
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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 abs_timeout);
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_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 abs_timeout expires, and the function shall
return the error [ETIMEDOUT].
The timeout shall expire when the absolute time specified by abs_timeout
passes, as measured by the clock upon which
timeouts are based (that is, when the value of that clock equals or
exceeds abs_timeout), or if the absolute time specified
by abs_timeout has already passed at the time of the call.
If the Timers option is supported, the timeout shall be based on
the CLOCK_REALTIME clock; if the Timers option
is not supported, the timeout shall be based on the system clock as
returned by the time() function. 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 abs_timeout 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
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
None.
SEE ALSO
posix_trace_create(), posix_trace_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, Copyright (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.opengroup.org/unix/online.html .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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