写csv相关操作_std::ios::trunc 追加写是什么

std::ios::in：输入模式，表示以读取方式打开流。
std::ios::out：输出模式。
std::ios::app：追加模式，表示以写入方式打开流，并将数据追加到文件末尾而不清除原有内容。
std::ios::trunc：截断模式，表示以写入方式打开流，并清除文件原有内容。
std::ios::binary：二进制模式，以二进制方式打开流。
std::ios::ate：打开流后将文件指针定位到文件末尾。

	//写csv  覆盖
	if (0) {
		std::ofstream outFile;
		outFile.open("t444est.csv", std::ios::out | std::ios::trunc);
		// 写入标题行



		outFile << "name" << ','
			<< "income" << ','
			<< "expenditure" << ','
			<< "addr" << std::endl;
		// ********写入两行数据*********
		// 写入字符串(数字)
		outFile << "zhangsan" << ','
			<< "3000" << ','
			<< "1200" << ','
			<< "中国 北京市" << std::endl;
		// 写入浮点数(转为字符串)
		outFile << "lisi" << ','
			<< std::to_string(2032.1) << ','
			<< std::to_string(789.2) << ','
			<< "中国 陕西省13333311" << std::endl;
		std::string name1="1222222";
		std::string name2="哈哈";
		std::string name3="asd好";
		CString name4;
		name4 = _T("号1111sad");
		outFile << name1 << ',';
		outFile << name2 << ',';
		outFile << name3 << ',';
		outFile << (CW2A)name4 << std::endl;



		outFile.close();
	}

	//写csv  不覆盖
	if (1) {
		std::ofstream outFile;
		outFile.open("t2est.csv", std::ios::app);
		// 写入标题行

		int a = 977676;

		outFile << "name" << ','
			<< "income" << ','
			<< "expenditure" << ','
			<< "addr" << std::endl;
		// ********写入两行数据*********
		// 写入字符串(数字)
		outFile << "" << ',' << "asfasf"
			<< a << ','
			<< "1200" << ','
			<< "中国"; 
		outFile << "北京asdasfasfsa市" << std::endl;
		// 写入浮点数(转为字符串)
		outFile << "lisi" << ','
			<< std::to_string(2032.1) << ','
			<< std::to_string(789.2) << ','
			<< "中国 陕西省13333311" << std::endl;
		std::string name1 = "1222222";
		std::string name2 = "哈哈";
		std::string name3 = "asd好";
		std::string name4 = "号sad";
		outFile << name1 << ',';
		outFile << name2 << ',';
		outFile << name3 << ',';
		outFile << name4 << std::endl;



		outFile.close();
	}


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