怎么把UDF计算数据的每一步写到TXT文档中？

中国范儿

网上找到这个， fp=fopen("data.txt","w");
printf("Writing UDF data to data file\n");
fprintf(fp,"time0 =%12.11f,force_x = %12.11f,force_y = %12.11f,force_yy = %12.11f\n", time0,force_x,force_y,force_yy);
fclose(fp);
可惜只能写最后一步的！