c++ parse argv

#include <iostream>
#include <format>

int main(int argc, char* argv[])
{
  if (argc > 1) {
    char prefix;
    char* opt;
    int valIndex;
    char* val;
    for (size_t i = 1; i < argc; i++)
    {
      prefix = *argv[i];
      if (prefix == '-')
      {
        opt = (argv[i] + 1);
        switch (*opt)
        {
        case 'i':
          valIndex = ++i;
          if (valIndex < argc) {
            val = argv[valIndex];
            std::cout << val << "\n";
          }
          break;
        case 'o':
          valIndex = ++i;
          if (valIndex < argc) {
            val = argv[valIndex];
            std::cout << val << "\n";
          }
          break;
        default:
          std::cout << std::format("Error:未知的选项 '{}'", argv[i]) << "\n";
          return 1;
        }
      }
      else
      {
        std::cout << std::format("Error:未知的前缀 '{}'", prefix) << "\n";
        return 1;
      }
    }
  }
  else
  {
    std::cout << std::format("没有参数") << "\n";
  }

  return 0;
}

测试:

> t.exe -i "input" -i "output"
input
output

> t.exe -a "asd.txt"
Error:未知的选项 '-a'

> t.exe -i "input" -i
input

> t.exe +i "input"
Error:未知的前缀 '+'