c++ - 参数检查

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main (int argc, char* argv[])
{
    string STRING;
    ifstream infile;
    STRING = argv[1];
    infile.open(argv[1]);
    if (infile.fail())// covers a miss spelling of a fail name
    {
        cout << "ERROR. Did you make a mistake in the Spelling of the File\n";
        return 1;
    }
    else
    {
        while(!infile.eof())
        {
            getline(infile,STRING); // Get the line
            cout<<STRING + "\n"; // Prints out File line
        }
        infile.close();
        return 0;
    }
}

除了一个问题，我的程序运行正常

如果用户只运行没有文件名的程序(我认为这是自变量)，例如./displayfile，则出现分段错误

我将如何修改我的代码，以使程序将退出并显示一条错误消息，如“添加文件名”

我的第一个想法是

if (!argc=2)
{
    cout << "ERROR. Enter a file name";
    return 1;
}

添加:
以防万一这很重要使用
g++ displayfile.cpp -o显示文件

最佳答案

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main (int argc, char* argv[]) {
   if(argc != 2) {
      cout << "You need to supply one argument to this program.";
      return -1;
   }

   string STRING;
   ifstream infile;
   STRING = argv[1];
   infile.open(argv[1]);
   if (infile.fail())// covers a miss spelling of a fail name {
      cout << "ERROR. Did you make a mistake in the Spelling of the File\n";
      return 1;
   }
   else {
      while(!infile.eof()) {
         getline(infile,STRING); // Get the line
         cout<<STRING + "\n"; // Prints out File line
      }
      infile.close();
      return 0;
   }
}