C++11文法

目錄

1.檔案流指針（輸入輸出）

方法1：substr截取字元串

方法2：boost::split()截取字元串

1.檔案流指針（輸入輸出）

【C++】C++ 檔案讀寫 ofstream和ifstream詳細用法 - bdy - 部落格園 (cnblogs.com)

方法1：substr截取字元串

#define FILENAME "C:\\Users\\xiao_\\Desktop\\text.csv"
#define FILENAME1 "C:\\Users\\xiao_\\Desktop\\text1.csv"
int main()
{
    std::list<std::string> StatYearList;
//從test.txt檔案讀取資料
    std::ifstream fin(FILENAME , std::ios::in);
    if (!fin.is_open()) 
    {
	    fmt::print( "error open file![{0}]\n", FILENAME);
	    return -1;
    }
    while (!fin.eof()) 
    {
	    std::string tmp;
	    std::string data;
	    IemsStatYear statYear;
		
	    getline(fin, tmp);
	    size_t star = tmp.find(',', 0);
	    if (star == std::string::npos)
	    {
		    fmt::print("找不到字元串[{0}]\n", star);
	    }
        statYear.year = stoi(tmp.substr(0, star));
	    star++;
	    statYear.devName = tmp.substr(star, tmp.find(',', star));
	    star++;
	    statYear.devType = tmp.substr(star, tmp.find(',', star));
	    star++;
        
        statYearList.push_back(statYear);
    }
    fin.close();

//輸出到另一個檔案test0.txt
    ofstream out(FILENAME1 , ios::out);
    out << "NAME,DATA_TYPE,DATA_MONTH,DATA_DAY,VAL,UNIT" << endl;
    for (int i = 0; i < statYearList.size(); i++) 
    {
		out << statYearList[i].NAME << "," << statYearList[i].DATA_TYPE << "," <<                                                     
          statYearList[i].DATA_MONTH << "," << statYearList[i].DATA_DAY << "," << 
                            statYearList[i].VAL << "," << statYearList[i].UNIT << endl;
	}
    out.close()

    return 0;
}
           

方法2：boost::split()截取字元串

用法：​​​​​​​

#include <boost/algorithm/string.hpp>

std::string line("a fox jump ");
// trim()， trim_left()， trim_right()
boost::trim(line);   // line: "a fox jump"

std::vector<std::string> contents;
// 分割，通過boost::is_any_of指定分割符。
boost::split(contents, line, boost::is_any_of(", "));
// 拼接
std::string line2 = boost::join(contents, "="); //line2: a=fox=jump
           

舉例：

int main()
{

    std::ifstream fin(fileName, std::ios::in);
    if (!fin.is_open())
    {
        fmt::print( "error open file![{0}]\n", fileName);
        return -1;
    }

    while (!fin.eof())
    {
        TYPE_iems_stat_year statYear;

        std::string tmp;
        getline(fin, tmp);

        std::vector<std::string> contents;
        boost::split(contents,tmp,boost::is_any_of(","));
        if(contents[0] == "")
        {
            return 0;
        }
        if(contents[0] == "year")
        {
            continue;
        }

        std::string sqlCmd = fmt::format("insert into iems_stat_year values ({},\"        {}\",\"{}\",\"{}\",\"{}\",{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{},{})",
                                         contents[0],contents[1],contents[2],contents[3],contents[4],contents[17],contents[5],contents[6],contents[7],contents[8],contents[9],
                                            contents[10],contents[11],contents[12],contents[13],contents[14],contents[15],contents[16],contents[18],contents[19],contents[20],contents[21]);

        StatYearList.push_back(sqlCmd);
        
    }

    fin.close();

    return 0;
}