POSIX_TRACE_GET_FILTER(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_get_filter, posix_trace_set_filter — retrieve and set the filter of an initialized trace stream (TRACING)

SYNOPSIS

#include <trace.h>

int posix_trace_get_filter(trace_id_t trid, trace_event_set_t *set);
int posix_trace_set_filter(trace_id_t trid,
    const trace_event_set_t *set, int how);

DESCRIPTION
The posix_trace_get_filter() function shall retrieve, into the argument pointed to by set, the actual trace event filter from the trace stream specified by trid.

The posix_trace_set_filter() function shall change the set of filtered trace event types after a trace stream identified by the trid argument is created. This function may be called prior to starting the trace stream, or while the trace stream is active. By default, if no call is made to posix_trace_set_filter(), all trace events shall be recorded (that is, none of the trace event types are filtered out).

If this function is called while the trace is in progress, a special system trace event, POSIX_TRACE_FILTER, shall be recorded in the trace indicating both the old and the new sets of filtered trace event types (see Table 2-4, Trace and Trace Event Filter Options: System Trace Events and Table 2-6, Trace, Trace Log, and Trace Event Filter Options: System Trace Events).

If the posix_trace_set_filter() function is interrupted by a signal, an error shall be returned and the filter shall not be changed. In this case, the state of the trace stream shall not be changed.

The value of the argument how indicates the manner in which the set is to be changed and shall have one of the following values, as defined in the <trace.h> header:

POSIX_TRACE_SET_EVENTSET
    The resulting set of trace event types to be filtered shall be the trace event type set pointed to by the argument set.

POSIX_TRACE_ADD_EVENTSET
    The resulting set of trace event types to be filtered shall be the union of the current set and the trace event type set pointed to by the argument set.

POSIX_TRACE_SUB_EVENTSET
    The resulting set of trace event types to be filtered shall be all trace event types in the current set that are not in the set pointed to by the argument set; that is, remove each element of the specified set from the current filter.

RETURN VALUE
Upon successful completion, these functions shall return a value of zero. Otherwise, they shall return the corresponding error number.

The posix_trace_get_filter() function stores the set of filtered trace event types in set, if successful.

ERRORS
These functions shall fail if:

EINVAL
    The value of the trid argument does not correspond to an active trace stream or the value of the argument pointed to by set is invalid.

EINTR
    The operation was interrupted by a signal.

The following sections are informative.

EXAMPLES
None.

APPLICATION USAGE
None.

RATIONALE
None.

FUTURE DIRECTIONS
The posix_trace_get_filter() and posix_trace_set_filter() functions may be removed in a future version.

SEE ALSO
Table 2-4, Trace and Trace Event Filter Options: System Trace Events, Table 2-6, Trace, Trace Log, and Trace Event Filter Options: System Trace Events, posix_trace_eventset_add()

The Base Definitions volume of POSIX.1-2017, <trace.h>

COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

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 .