string ReadLine(char *filename,int line)
{
    int i=0;
    string temp;
    fstream file;
    file.open(filename,ios::in);
    
    if(line<=0)
    {
        return "Error 1: 行数错误，不能为0或负数。";
    }
    
    if(file.fail())
    {
        return "Error 2: 文件不存在。";
    }

    while(getline(file,temp)&&i<line-1)
    {
        i++;
    }
    
    file.close();
    return temp;
}

int _tmain(int argc, _TCHAR* argv[])
{
	// 初始化
	string exePath = ReadLine("parameter.txt",1);
	string command1 = ReadLine("parameter.txt",2);
	string command2 = ReadLine("parameter.txt",3);
	cout << "命令格参数：" <<endl;
	cout << exePath << endl;
	cout << command1 << endl;
	cout << command2 << endl;
	
	
	getchar();
	return 0;
}

效果图：

1. vs2019，Unicode，C++
2. 代码：

   #pragma once
   #include <afxwin.h>
   #include <iostream>
   #include <cstring>
   #include <string>
   #include <fstream>  
   #include <direct.h>
   
   
   bool GetTxtValue(_In_ string sKey,_Out_ string * strTxtValue)
   {
   	USES_CONVERSION;
   	char cWorkPath[MAX_PATH];						 // 工作目录
   	char cLineBuffer[MAX_PATH];
   	string sAppConfig;							 // AppConfig.txt 路径，用于读
   	string sLineBuffer;
   	int iPtr = 0;
   	BOOL bFindKey = FALSE;
   	ifstream ifAppConfig;
   
   	getcwd(cWorkPath, MAX_PATH);
   	sAppConfig = cWorkPath;
   	sAppConfig = sAppConfig + "\\AppConfig.txt";
   
   	ifAppConfig.open(sAppConfig.c_str(), ios::in | ios::binary);
   
   	if (ifAppConfig.is_open())
   	{
   		while (ifAppConfig.getline(cLineBuffer, MAX_PATH))								// 获取 sKey 所在行
   		{
   			sLineBuffer = cLineBuffer;
   			if (string::npos != sLineBuffer.find(sKey)) 								// 找到关键词
   			{
   				iPtr = sLineBuffer.find(sKey);											// 获取 sKey 所在的下标
   				*strTxtValue = sLineBuffer.substr(iPtr + sKey.size() + 1, sLineBuffer.size());	// 获取路径
   				bFindKey = TRUE;
   			}
   		}
   	}
   	else
   	{
   		// 没有打开文件
   		MessageBox(_T("打开文件失败，请检查路径"));
   		return NULL;
   	}
   	ifAppConfig.close();
   
   	return true;
   }

3. 说明：该代码读取AppConfig.txt，第一个参数为AppConfig.txt中的关键词；第二个参数是获取关键词所在行的内容（不包括关键词本身）。
   
   AppConfig.txt内容如下，每一行空格前是关键词，空格后是对应的值。
   

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

struct game
{
	int num;
	int year;
	float arr[3];
};

struct gj
{
    int a;
    game dz;
};

int count_lines(char *filename) {
    int n = 0;
    ifstream ReadFile;
    string tmp;
    ReadFile.open(filename,ios::in);
    if(ReadFile.fail())
    {
        return 0;
    }
    else
    {
        while (getline(ReadFile, tmp, '\n'))
        {
            n++;
        }
        ReadFile.close();
        cout<<"the rows of txt = " << n<<endl;
        return n;
    }
    

}

int main()
{
    char filename[] = "g1.txt";
    fstream file;
    file.open(filename,ios::in);
    ifstream myfile(filename);
    game g2;
    gj gj1;
    // if(!myfile.is_open())
    // {
    //     cout << "can not open this file" << endl;
    //     return 0;
    // }

    //int row = count_lines("g1.txt");

    if (file.fail())
    {
        cout<< "file not exit"<<endl;
        return 0;
    }

    string s ;
    int line = 4;
    int i = 0;
    // myfile >> gj1.dz.num >>gj1.dz.year >>gj1.dz.arr[0]>>gj1.dz.arr[1]>>gj1.dz.arr[2];
    // cout << "value = " << gj1.dz.year;
    while (getline(myfile,s)&&i < line-2)
    {
        i++;
    }
    myfile >> gj1.dz.num >>gj1.dz.year >>gj1.dz.arr[0]>>gj1.dz.arr[1]>>gj1.dz.arr[2];
    //myfile >> g2.num >> g2.year >> g2.arr[0] >>g2.arr[1]>>g2.arr[2];
    cout << "value = " << gj1.dz.year;
    cout <<" value g2 = " <<gj1.dz.arr[0]<<endl;
    int years = gj1.dz.year;
    cout << years;
    myfile.close();
    return 0;
}