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====== DosSysTrace ======

===== Brief =====


Writes a trace record to the system trace buffer. It provides a high speed event recording mechanism which may be used by PM and non-PM threads in ring 3 and ring 2 and by detached processes.

===== Syntax =====
<code c>
 APIRET APIENTRY16 DosSysTrace
        (USHORT major, USHORT cBuffer, USHORT minor, PCHAR pBuffer) 
</code>

===== Parameters =====

  * major (USHORT) input : Major code which identifies the trace record. Range reserved for user is 245-255. Valid range 0-255 
  * cBuffer (USHORT) input : Length of optional buffer. Valid range
    *0 - 512 (before 4.0 FP 10 and 3.0 FP 35)
    *0 - 4099 (from 3.0 FP35 and 4.0 FP10 onwards).
  * minor (USHORT) input : Minor code which identifies the trace record. Major-minor code pair should uniquely identify the trace record. Valid range 1 - 255
  * pBuffer (PCHAR) input : Pointer to optional buffer. If cBuffer is 0, then pBuffer is ignored.

===== Return Code =====

ulrc (APIRET) returns

DosSysTrace returns one of the following values

  * 0  NO_ERROR
  * 150 ERROR_SYSTEM_TRACE

===== Remarks =====

DosSysTrace creates a trace record that includes the following items:

  * Header Major code, minor code, time stamp, PID of logging process
  * Optional System Data Controlled by the TRACE command
  * Optional User Data Specified by the pBuffer parameter 

To check is tracing enabled use [[DosGetInfoSeg]]. GlobalInfoSeg contains 256bit flags area. See [[DosGetInfoSeg]] for more info.

===== Example Code =====

<code c>
int main(int argc, char *argv[], char *envp[]){
   APIRET rc=0;          /* default return code */
   USHORT major=255;       /* default major code */
   USHORT minor=1;         /* default minor code */
   USHORT cBuffer=0;       /* default buffer length */
   PCHAR  pBuffer=NULL;    /* default buffer address */

   if (argc>1)
   {
      pBuffer = argv[1];
      cBuffer = strlen(argv[1]);
   }

   if (argc>2) major = atol(argv[2]);
   if (argc>3) minor = atol(argv[3]);

   rc = Dos16SysTrace(major, cBuffer, minor, pBuffer);

   if (rc) printf("DosSysTrace retuned rc=%u\n", rc);

   return rc;
}
</code>

===== Related Functions =====


  * [[DosDumpProcess]]
  * [[DosForceSystemDump]]

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