.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved .TH "POSIX_TRACE_GETNEXT_EVENT" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" .\" posix_trace_getnext_event .SH NAME posix_trace_getnext_event, posix_trace_timedgetnext_event, posix_trace_trygetnext_event \- retrieve a trace event (\fBTRACING\fP) .SH SYNOPSIS .LP \fB#include .br #include .br .sp int posix_trace_getnext_event(trace_id_t\fP \fItrid\fP\fB, .br \ \ \ \ \ \ struct posix_trace_event_info *restrict\fP \fIevent\fP\fB, .br \ \ \ \ \ \ void *restrict\fP \fIdata\fP\fB, size_t\fP \fInum_bytes\fP\fB, .br \ \ \ \ \ \ size_t *restrict\fP \fIdata_len\fP\fB, int *restrict\fP \fIunavailable\fP\fB); .br \fP .LP \fBint posix_trace_timedgetnext_event(trace_id_t\fP \fItrid\fP\fB, .br \ \ \ \ \ \ struct posix_trace_event_info *restrict\fP \fIevent\fP\fB, .br \ \ \ \ \ \ void *restrict\fP \fIdata\fP\fB, size_t\fP \fInum_bytes\fP\fB, .br \ \ \ \ \ \ size_t *restrict\fP \fIdata_len\fP\fB, int *restrict\fP \fIunavailable\fP\fB, .br \ \ \ \ \ \ const struct timespec *restrict\fP \fIabs_timeout\fP\fB); .br \fP .LP \fBint posix_trace_trygetnext_event(trace_id_t\fP \fItrid\fP\fB, .br \ \ \ \ \ \ struct posix_trace_event_info *restrict\fP \fIevent\fP\fB, .br \ \ \ \ \ \ void *restrict\fP \fIdata\fP\fB, size_t\fP \fInum_bytes\fP\fB, .br \ \ \ \ \ \ size_t *restrict\fP \fIdata_len\fP\fB, int *restrict\fP \fIunavailable\fP\fB); \fP \fB .br \fP .SH DESCRIPTION .LP The \fIposix_trace_getnext_event\fP() function shall report a recorded trace event either from an active trace stream without log \ or a pre-recorded trace stream identified by the \fItrid\fP argument. The \fIposix_trace_trygetnext_event\fP() function shall report a recorded trace event from an active trace stream without log identified by the \fItrid\fP argument. .LP The trace event information associated with the recorded trace event shall be copied by the function into the structure pointed to by the argument \fIevent\fP and the data associated with the trace event shall be copied into the buffer pointed to by the \fIdata\fP argument. .LP The \fIposix_trace_getnext_event\fP() function shall block if the \fItrid\fP 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 \fIunavailable\fP argument shall be set to zero. Otherwise, the variable pointed to by the \fIunavailable\fP argument shall be set to a value different from zero. .LP \ The \fIposix_trace_timedgetnext_event\fP() function shall attempt to get another trace event from an active trace stream without log, as in the \fIposix_trace_getnext_event\fP() 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 \fIabs_timeout\fP expires, and the function shall return the error [ETIMEDOUT]. .LP The timeout shall expire when the absolute time specified by \fIabs_timeout\fP passes, as measured by the clock upon which timeouts are based (that is, when the value of that clock equals or exceeds \fIabs_timeout\fP), or if the absolute time specified by \fIabs_timeout\fP has already passed at the time of the call. .LP \ 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 \fItime\fP() function. The resolution of the timeout shall be the resolution of the clock on which it is based. The \fBtimespec\fP data type is defined in the \fI\fP header. .LP 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 \fIabs_timeout\fP argument need not be checked if a trace event is immediately available from the trace stream. .LP The behavior of this function for a pre-recorded trace stream is unspecified. .LP The \fIposix_trace_trygetnext_event\fP() function shall not block. \ This function shall return an error if the \fItrid\fP argument identifies a pre-recorded trace stream. If a recorded trace event was reported, the variable pointed to by the \fIunavailable\fP argument shall be set to zero. Otherwise, if no trace event was reported, the variable pointed to by the \fIunavailable\fP argument shall be set to a value different from zero. .LP The argument \fInum_bytes\fP shall be the size of the buffer pointed to by the \fIdata\fP argument. The argument \fIdata_len\fP reports to the application the length in bytes of the data record just transferred. If \fInum_bytes\fP is greater than or equal to the size of the data associated with the trace event pointed to by the \fIevent\fP argument, all the recorded data shall be transferred. In this case, the \fItruncation-status\fP 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 \fInum_bytes\fP argument is less than the length of recorded trace event data, the data transferred shall be truncated to a length of \fInum_bytes\fP, the value stored in the variable pointed to by \fIdata_len\fP shall be equal to \fInum_bytes\fP, and the \fItruncation-status\fP member of the \fIevent\fP structure argument shall be set to POSIX_TRACE_TRUNCATED_READ (see the \fBposix_trace_event_info\fP structure defined in \fI\fP). .LP 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. .SH RETURN VALUE .LP Upon successful completion, these functions shall return a value of zero. Otherwise, they shall return the corresponding error number. .LP If successful, these functions store: .IP " *" 3 The recorded trace event in the object pointed to by \fIevent\fP .LP .IP " *" 3 The trace event information associated with the recorded trace event in the object pointed to by \fIdata\fP .LP .IP " *" 3 The length of this trace event information in the object pointed to by \fIdata_len\fP .LP .IP " *" 3 The value of zero in the object pointed to by \fIunavailable\fP .LP .SH ERRORS .LP These functions shall fail if: .TP 7 .B EINVAL The trace stream identifier argument \fItrid\fP is invalid. .sp .LP The \fIposix_trace_getnext_event\fP() and \fIposix_trace_timedgetnext_event\fP() functions shall fail if: .TP 7 .B EINTR The operation was interrupted by a signal, and so the call had no effect. .sp .LP The \fIposix_trace_trygetnext_event\fP() function shall fail if: .TP 7 .B EINVAL The trace stream identifier argument \fItrid\fP does not correspond to an active trace stream. .sp .LP The \fIposix_trace_timedgetnext_event\fP() function shall fail if: .TP 7 .B EINVAL There is no trace event immediately available from the trace stream, and the \fItimeout\fP argument is invalid. .TP 7 .B ETIMEDOUT No trace event was available from the trace stream before the specified timeout \fItimeout\fP expired. .sp .LP \fIThe following sections are informative.\fP .SH EXAMPLES .LP None. .SH APPLICATION USAGE .LP None. .SH RATIONALE .LP None. .SH FUTURE DIRECTIONS .LP None. .SH SEE ALSO .LP \fIposix_trace_create\fP() , \fIposix_trace_open\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI\fP, \fI\fP .SH 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 .