[VxWorks] vxworks fopen fwrite

void writeb( void )
{
   FILE *stream;
   char list[30],lista[30];
   int  i, numread, numwritten;

   /* Open file in text mode: */
   if( (stream = fopen( "host:d:/temp/tstf/a.txt", "w+b" )) != NULL )
   {
      for ( i = 0; i < 25; i++ )
         list = (char)('z' - i);
      /* Write 25 characters to stream */
      numwritten = fwrite( list, sizeof( char ), 25, stream );
      printf( "Wrote %d items\n", numwritten );   
      fclose( stream );

   }
   else
      printf( "Problem opening the file\n" );

   if( (stream = fopen( "host:d:/temp/tstf/a.txt", "r+b" )) != NULL )
   {
      /* Attempt to read in 25 characters */
      numread = fread( lista, sizeof( char ), 25, stream );
      printf( "Number of items read = %d\n", numread );
      printf( "Contents of buffer = %.25s\n", lista );
      fclose( stream );
   }
   else
      printf( "File could not be opened\n" );
}

将程序下到vxsim里面，shell运行writeb，显示写文件25个字节成功，写完后再fopen for read 也成功，但是没有读回数据；在指定位置也没有找到创建的文件。。


请问是怎么回事？