把字符串数字转成uint64_t类型

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <sstream>
using namespace std;

int main(int argc, char **argv)
{
     if (argc < 2)
    {
        cerr<<"Usage: transfernum num"<<endl;
        return -1;
    }

cout<<"Input Num:"<<argv[1]<<endl;

unsigned long long ullNum1 = 0, ullNum2=0, ullNum3=0, ullNum4=0;

ullNum1 = atoi(argv[1]);

ullNum2 = atol(argv[1]);

ullNum3 = atoll(argv[1]);

ullNum4 = strtoull(argv[1], NULL, 10);

cout<<"transfer by atoi: "<<ullNum1<<endl;
cout<<"transfer by atol: "<<ullNum2<<endl;
cout<<"transfer by atoll: "<<ullNum3<<endl;
cout<<"transfer by strtoull: "<<ullNum4<<endl;

 

//这个方法是在网上找的，这里测试下是否管用
stringstream strValue;
strValue<<argv[1];
unsigned long long value;
strValue << value;
cout<<value<<endl;

return 0;
}

 

g++ main.cpp -o transfernum

./transfernum 18446744073709551615  (这个值是2^64-1，即64位的最大值)

输出：

Input Num:18446744073709551615      
transfer by atoi: 18446744073709551615     (atoi也正确了？奇怪)
transfer by atol: 9223372036854775807
transfer by atoll: 9223372036854775807
transfer by strtoull: 18446744073709551615  
4196992        （使用网上找的方法发现不正确）