如何将 char c[0] 转移到 int

Question

I read a file with getline, and want to transfer char c[0] to int, I got an error.

error: invalid conversion from ‘char’ to ‘const char*’ [-fpermissive]
g[n].chicken = atoi(c[0]);
                       ^

In file included from assign.cpp:5:0: /usr/include/stdlib.h:147:12: error: initializing argument 1 of 'int atoi(const char*)' [-fpermissive] extern int atoi (const char *__nptr)

 24        int g;
 25        string str;
 26        while(getline(file,str)){
 27           
 28           const char* ct = str.c_str();
 29           char c[5];
 30           strcpy(c,ct);
 31        
 32
 33           g = atoi(c[0]);

Answer 1

The declaration of atoi looks like this: int atoi(const char* buffer)

You need

g = atoi(c);

because c is the pointer to the character array. The array c[5] consists of 5 bytes. c[0] is the first byte. c alone is interpreted by the compiler as a pointer to the first byte.

So, atoi() it takes a pointer to an array of characters. You passed it the first character.

Using std::getline() to retrieve user input is a great idea. Learn to use stringstream to parse items from the getline(). Once you get good at it, you will make fewer mistakes:

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

int main()
{
  int g;

  std::ifstream file;
  file.open ("example.txt");

  std::string str;
  while (getline(file, str)) {
    std::istringstream stream(str);

    stream >> g;

    std::cout << "g is " << g << std::endl;

  }
}