qnx_trace_info()

return information from a trace buffer

Synopsis:

#include <sys/trace.h>
int qnx_trace_info( pid_t proc_pid,
                    struct _trace_info *info );

The qnx_trace_info() function returns information from the trace buffer located on the node whose process manager is addressed by proc_pid. The _trace_info structure contains at least the following members:

long buffsize: The size of the trace buffer
long datasize: The amount of data in the trace buffer
unsigned short overruns: The current number of overruns
unsigned short severity: The minimum severity level to be logged
pid_t reader: If another process is currently doing a qnx_trace_read(), then the reader member contains its process id; otherwise, this field is zero.
unsigned short tracesel: The segment of the trace buffer
long hi_water: The number of bytes required to be in the trace buffer before the proxy is triggered
pid_t proxy: The proxy to be triggered

If proc_pid is zero or PROC_PID, the trace buffer on the current node is accessed. To access a trace buffer on another node, you must establish a virtual circuit to the process manager on that node and pass the vid as proc_pid.

Returns:

0: Success
-1: An error occurred. errno is set to indicate the error.

Errors:

ENOSYS: The process manager doesn't support trace calls.
ESRCH: The proc_pid is invalid.

Examples:

/*
 * Display the trace info
 */
#include <stdio.h>
#include <errno.h>
#include <sys/trace.h>

void main()
  {
    struct _trace_info info;

    if( qnx_trace_info( 0, &info ) == -1 ) {
      perror( "trace_info" );
    } else {
      printf( "overruns = %u\n", info.overruns );
      printf( "severity = %d\n", info.severity );
      printf( "reader   = %d\n", info.reader );
      printf( "buffsize = %ld\n", info.buffsize );
      printf( "datasize = %ld\n", info.datasize );
      printf( "tracesel = %04X\n", info.tracesel );
      printf( "hi_water = %ld\n", info.hi_water );
      printf( "proxy    = %d\n", info.proxy );
    }
  }

Classification:

QNX

Safety:
Interrupt handler	No
Signal handler	Yes, but modifies errno
Thread	Yes