POSIX_TRACE_CREATE(3)      POSIX Programmer's Manual     POSIX_TRACE_CREATE(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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 .



IEEE/The Open Group                  2017                POSIX_TRACE_CREATE(3)
