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.TH POSIX_TRACE_GET_FILTER "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_get_filter,
posix_trace_set_filter
\(em retrieve and set the filter of an initialized trace stream
(\fBTRACING\fP)
.SH SYNOPSIS
.LP
.nf
#include <trace.h>
.P
int posix_trace_get_filter(trace_id_t \fItrid\fP, trace_event_set_t *\fIset\fP);
int posix_trace_set_filter(trace_id_t \fItrid\fP,
    const trace_event_set_t *\fIset\fP, int \fIhow\fP);
.fi
.SH DESCRIPTION
The
\fIposix_trace_get_filter\fR()
function shall retrieve, into the argument pointed to by
.IR set ,
the actual trace event filter from the trace stream specified by
.IR trid .
.P
The
\fIposix_trace_set_filter\fR()
function shall change the set of filtered trace event types after a
trace stream identified by the
.IR 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
\fIposix_trace_set_filter\fR(),
all trace events shall be recorded (that is, none of the trace event
types are filtered out).
.P
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
.IR "Table 2-4" ", " "Trace and Trace Event Filter Options: System Trace Events"
and
.IR "Table 2-6" ", " "Trace" ", " "Trace Log" ", " "and Trace Event Filter Options: System Trace Events").
.P
If the
\fIposix_trace_set_filter\fR()
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.
.P
The value of the argument
.IR how
indicates the manner in which the set is to be changed and shall have
one of the following values, as defined in the
.IR <trace.h> 
header:
.IP POSIX_TRACE_SET_EVENTSET 6
.br
The resulting set of trace event types to be filtered shall be the
trace event type set pointed to by the argument
.IR set .
.IP POSIX_TRACE_ADD_EVENTSET 6
.br
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
.IR set .
.IP POSIX_TRACE_SUB_EVENTSET 6
.br
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
.IR set ;
that is, remove each element of the specified set from the current
filter.
.SH "RETURN VALUE"
Upon successful completion, these functions shall return a value of
zero. Otherwise, they shall return the corresponding error number.
.P
The
\fIposix_trace_get_filter\fR()
function stores the set of filtered trace event types in
.IR set ,
if successful.
.SH ERRORS
These functions shall fail if:
.TP
.BR EINVAL
The value of the
.IR trid
argument does not correspond to an active trace stream or the value of
the argument pointed to by
.IR set
is invalid.
.TP
.BR EINTR
The operation was interrupted by a signal.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
The
\fIposix_trace_get_filter\fR()
and
\fIposix_trace_set_filter\fR()
functions may be removed in a future version.
.SH "SEE ALSO"
.ad l
.IR "Table 2-4" ", " "Trace and Trace Event Filter Options: System Trace Events",
.IR "Table 2-6" ", " "Trace" ", " "Trace Log" ", " "and Trace Event Filter Options: System Trace Events",
.IR "\fIposix_trace_eventset_add\fR\^(\|)"
.ad b
.P
The Base Definitions volume of POSIX.1\(hy2008,
.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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