C++:“char*”vs“char”,尝试分配变量时出错

我正在为编程I课做作业。我是C++的新手。我们要做的是获取用户在执行时提供的年、月和日参数,并计算它们与当前日期之间的差值。

在我的主函数中,我有以下代码从用户那里获取这些参数:

int main(int argc, char** argv)

我的理解是,这将创建一个字符数组并在其中存储用户的参数。接下来,我将存储在此数组中的参数分配给新的char变量,以便将它们传递给函数,如下所示:

int main(int argc, char** argv)
{
    int year, month, day;
    char arg1 = argv[1];
    string arg2 = argv[2];
    char arg3 = argv[3];

    argumentChange(argc, arg1, arg2, arg3, year, month, day);

blablabla other code
}

哪里 argumentChange 是我将它们发送到的函数。问题是,当我尝试编译此文件时,我收到以下错误:

错误:从“char*”到“char”[-fpermissive]的转换无效

字符arg1=argv[1];

错误:从“char*”到“char”[-fpermissive]的转换无效

charArg3=argv[3];

我已经试着寻找这个问题,但我真的无法理解其他地方给出的解释。我看到很多人提到了“指针”,这是我们在课堂上还没有讨论过的,我对此一无所知。我做错了什么?我该怎么做?

以下是我整个程序的完整代码:

#include <iostream>
#include <ctime>
#include <string>

using namespace std;

void argumentChange(int numArg, char chArg1, string sArg2, char chArg3, int year, int month, int day)
{
    cout << "Starting birth date: " << chArg1 << " " << sArg2 << " " << chArg3
         << endl;
    if (numArg < 4 || numArg > 4)
    {
        cout << "Correct Usage: ./cl <birth_year><birth_month><birth_day>" << endl;
        cout << "Try again, dude." << endl;
    }
    else if (numArg == 4)
    {
        year = chArg1 - '0';
        day = chArg3 - '0';
        if ((sArg2 == "january") || (sArg2 == "January"))
        {
        month = 0;
        }
        else if ((sArg2 == "february") || (sArg2 == "February"))
        {
            month = 1;
        }
        else if ((sArg2 == "march") || (sArg2 == "March"))
        {
            month = 2;
        }
        else if ((sArg2 == "april") || (sArg2 == "April"))
        {
            month = 3;
        }
        else if ((sArg2 == "may") || (sArg2 == "May"))
        {
            month = 4;
        }
        else if ((sArg2 == "june") || (sArg2 == "June"))
        {
            month = 5;
        }
        else if ((sArg2 == "july") || (sArg2 == "July"))
        {
            month = 6;
        }
        else if ((sArg2 == "august") || (sArg2 == "August"))
        {
            month = 7;
        }
        else if ((sArg2 == "september") || (sArg2 == "September"))
        {
            month = 8;
        }
        else if ((sArg2 == "october") || (sArg2 == "October"))
        {
            month = 9;
        }
        else if ((sArg2 == "november") || (sArg2 == "November"))
        {
            month = 10;
        }
        else if ((sArg2 == "december") || (sArg2 == "December"))
        {
            month = 11;
        }
        else
        {
                cout << "Error: You have entered an invalid term for month.  Please type ";
                cout << "the complete name of a valid month." << endl;
        }
    }
}

struct tm bday(int year, int month, int day)
    {
        struct tm r {0};
    
        r.tm_year = year - 1900;
        r.tm_mon = month;
        r.tm_mday = day;
    
        return r;
    }

int main(int argc, char** argv)
{
    int year, month, day;
    char arg1 = argv[1];
    string arg2 = argv[2];
    char arg3 = argv[3];

    argumentChange(argc, arg1, arg2, arg3, year, month, day);

    struct tm a = bday(year, month, day);
    time_t x = mktime(&a);
    time_t y = time(0);
    if ( x != (time_t)(-1) && y != (time_t)(-1) )
    {
        double difference = difftime(y, x) / (60 * 60 * 24);
        cout << ctime(&x);
        cout << ctime(&y);
        cout << "difference = " << difference << " days" << endl;
    }
    return 0;
}