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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_create,  posix_trace_create_withlog, posix_trace_flush, posix_trace_shutdown —
       trace stream initialization, flush, and shutdown from a process (TRACING)

SYNOPSIS

       #include <sys/types.h>
       #include <trace.h>

       int posix_trace_create(pid_t pid,
           const trace_attr_t *restrict attr,
           trace_id_t *restrict trid);
       int posix_trace_create_withlog(pid_t pid,
           const trace_attr_t *restrict attr, int file_desc,
           trace_id_t *restrict trid);
       int posix_trace_flush(trace_id_t trid);
       int posix_trace_shutdown(trace_id_t trid);

DESCRIPTION

       The posix_trace_create() function shall create an active trace stream.  It  allocates  all
       the  resources  needed by the trace stream being created for tracing the process specified
       by pid in accordance with the attr argument. The  attr  argument  represents  the  initial
       attributes  of  the  trace  stream  and  shall  have  been  initialized  by  the  function
       posix_trace_attr_init() prior to the posix_trace_create() call. If the  argument  attr  is
       NULL,  the  default  attributes  shall  be  used.  The  attr  attributes  object  shall be
       manipulated through a set  of  functions  described  in  the  posix_trace_attr  family  of
       functions.  If  the  attributes  of  the object pointed to by attr are modified later, the
       attributes of the trace stream shall not be affected. The creation-time attribute  of  the
       newly  created  trace  stream shall be set to the value of the system clock, if the Timers
       option is not supported, or to the value of the CLOCK_REALTIME clock, if the Timers option
       is supported.

       The pid argument represents the target process to be traced. If the process executing this
       function does not have appropriate privileges to trace the process identified by  pid,  an
       error shall be returned. If the pid argument is zero, the calling process shall be traced.

       The posix_trace_create() function shall store the trace stream identifier of the new trace
       stream in the object pointed to by the trid argument. This trace stream  identifier  shall
       be  used in subsequent calls to control tracing. The trid argument may only be used by the
       following functions:

       posix_trace_clear()                      posix_trace_getnext_event()
       posix_trace_eventid_equal()              posix_trace_shutdown()
       posix_trace_eventid_get_name()           posix_trace_start()
       posix_trace_eventtypelist_getnext_id()   posix_trace_stop()
       posix_trace_eventtypelist_rewind()       posix_trace_timedgetnext_event()
       posix_trace_get_attr()                   posix_trace_trid_eventid_open()
       posix_trace_get_status()                 posix_trace_trygetnext_event()

       If the Trace Event Filter option is supported, the following additional functions may  use
       the trid argument:

       posix_trace_get_filter()   posix_trace_set_filter()

       In  particular, notice that the operations normally used by a trace analyzer process, such
       as posix_trace_rewind() or posix_trace_close(), cannot be invoked using the  trace  stream
       identifier returned by the posix_trace_create() function.

       A trace stream shall be created in a suspended state.  If the Trace Event Filter option is
       supported, its trace event type filter shall be empty.

       The posix_trace_create() function may be called multiple times from the same or  different
       processes,   with   the  system-wide  limit  indicated  by  the  runtime  invariant  value
       {TRACE_SYS_MAX}, which has the minimum value {_POSIX_TRACE_SYS_MAX}.

       The trace stream identifier returned by the posix_trace_create() function in the  argument
       pointed to by trid is valid only in the process that made the function call. If it is used
       from another process, that is a child process, in functions defined in POSIX.1‐2008, these
       functions shall return with the error [EINVAL].

       The  posix_trace_create_withlog()  function  shall  be equivalent to posix_trace_create(),
       except that it associates a trace log with this stream. The file_desc  argument  shall  be
       the file descriptor designating the trace log destination. The function shall fail if this
       file descriptor refers to a file with a file type that is  not  compatible  with  the  log
       policy  associated  with  the  trace  log. The list of the appropriate file types that are
       compatible with each log policy is implementation-defined.

       The posix_trace_create_withlog() function shall return in the parameter pointed to by trid
       the trace stream identifier, which uniquely identifies the newly created trace stream, and
       shall be used in subsequent calls to control tracing. The trid argument may only  be  used
       by the following functions:

       posix_trace_clear()                      posix_trace_get_status()
       posix_trace_eventid_equal()              posix_trace_getnext_event()
       posix_trace_eventid_get_name()           posix_trace_shutdown()
       posix_trace_eventtypelist_getnext_id()   posix_trace_start()
       posix_trace_eventtypelist_rewind()       posix_trace_stop()
       posix_trace_flush()                      posix_trace_timedgetnext_event()
       posix_trace_get_attr()                   posix_trace_trid_eventid_open()

       If  the Trace Event Filter option is supported, the following additional functions may use
       the trid argument:

       posix_trace_get_filter()   posix_trace_set_filter()

       In particular, notice that the operations normally used by a trace analyzer process,  such
       as  posix_trace_rewind()  or posix_trace_close(), cannot be invoked using the trace stream
       identifier returned by the posix_trace_create_withlog() function.

       The posix_trace_flush() function  shall  initiate  a  flush  operation  which  copies  the
       contents of the trace stream identified by the argument trid into the trace log associated
       with the trace stream at the creation time. If no trace log has been associated  with  the
       trace  stream  pointed to by trid, this function shall return an error. The termination of
       the flush operation can be polled by the  posix_trace_get_status()  function.  During  the
       flush  operation,  it shall be possible to trace new trace events up to the point when the
       trace stream becomes full.  After flushing is completed, the space  used  by  the  flushed
       trace events shall be available for tracing new trace events.

       If  flushing the trace stream causes the resulting trace log to become full, the trace log
       full policy shall be applied. If the trace log-full-policy attribute is set, the following
       occurs:

       POSIX_TRACE_UNTIL_FULL
             The trace events that have not yet been flushed shall be discarded.

       POSIX_TRACE_LOOP
             The trace events that have not yet been flushed shall be written to the beginning of
             the trace log, overwriting previous trace events stored there.

       POSIX_TRACE_APPEND
             The trace events that have not yet been flushed shall be appended to the trace log.

       The posix_trace_shutdown() function shall stop the tracing of trace events  in  the  trace
       stream   identified   by   trid,   as   if   posix_trace_stop()   had  been  invoked.  The
       posix_trace_shutdown() function shall free all the resources  associated  with  the  trace
       stream.

       The  posix_trace_shutdown()  function  shall not return until all the resources associated
       with the trace stream have been freed. When the posix_trace_shutdown()  function  returns,
       the  trid  argument  becomes  an  invalid trace stream identifier. A call to this function
       shall unconditionally deallocate the resources regardless of whether all trace events have
       been   retrieved   by   the   analyzer   process.   Any  thread  blocked  on  one  of  the
       trace_getnext_event() functions (which specified this trid) before this call is  unblocked
       with the error [EINVAL].

       If  the process exits, invokes a member of the exec family of functions, or is terminated,
       the trace streams that the process had created and that have not yet been shut down, shall
       be  automatically shut down as if an explicit call were made to the posix_trace_shutdown()
       function.

       For an active trace stream with log, when the posix_trace_shutdown() function  is  called,
       all  trace  events that have not yet been flushed to the trace log shall be flushed, as in
       the posix_trace_flush() function, and the trace log shall be closed.

       When a trace log is closed, all the information that may be retrieved later from the trace
       log through the trace interface shall have been written to the trace log. This information
       includes the trace attributes, the list of trace event types  (with  the  mapping  between
       trace event names and trace event type identifiers), and the trace status.

       In  addition, unspecified information shall be written to the trace log to allow detection
       of a valid trace log during the posix_trace_open() operation.

       The posix_trace_shutdown() function shall not return until  all  trace  events  have  been
       flushed.

RETURN VALUE

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

       The posix_trace_create() and posix_trace_create_withlog() functions store the trace stream
       identifier value in the object pointed to by trid, if successful.

ERRORS

       The posix_trace_create() and posix_trace_create_withlog() functions shall fail if:

       EAGAIN No more trace streams can be started now.  {TRACE_SYS_MAX} has been exceeded.

       EINTR  The operation was interrupted by a signal. No trace stream was created.

       EINVAL One or more of the trace parameters specified by the attr parameter is invalid.

       ENOMEM The  implementation  does  not currently have sufficient memory to create the trace
              stream with the specified parameters.

       EPERM  The caller does not have appropriate privileges to trace the process  specified  by
              pid.

       ESRCH  The pid argument does not refer to an existing process.

       The posix_trace_create_withlog() function shall fail if:

       EBADF  The file_desc argument is not a valid file descriptor open for writing.

       EINVAL The  file_desc argument refers to a file with a file type that does not support the
              log policy associated with the trace log.

       ENOSPC No space left on device. The device corresponding to the  argument  file_desc  does
              not contain the space required to create this trace log.

       The posix_trace_flush() and posix_trace_shutdown() functions shall fail if:

       EINVAL The  value  of the trid argument does not correspond to an active trace stream with
              log.

       EFBIG  The trace log file has attempted to exceed an implementation-defined  maximum  file
              size.

       ENOSPC No space left on device.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       The    posix_trace_create(),    posix_trace_create_withlog(),   posix_trace_flush(),   and
       posix_trace_shutdown() functions may be removed in a future version.

SEE ALSO

       clock_getres(), exec, posix_trace_attr_destroy(), posix_trace_clear(),
       posix_trace_close(), posix_trace_eventid_equal(), posix_trace_eventtypelist_getnext_id(),
       posix_trace_get_attr(), posix_trace_get_filter(), posix_trace_getnext_event(),
       posix_trace_start(), posix_trace_start(), time()

       The Base Definitions volume of POSIX.1‐2017, <sys_types.h>, <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 .