C++ read函数读入int整形数据

Read函数定义

通过read函数将文件中的数据按照一定的长度读取出来并且存放在新的数组中。用于从文件中读取数据。

函数原型istream& read (char* s, streamsize n);

参数char* s取出数据的流向的char类型数组指针，streamsize n表示数组的长度

#include<iostream>
using namespace std;
int read()//read函数主体部分
{
  int x=0,f=1;char ch=getchar();
  while(ch<'0'||ch>'9')
  {
    if(ch=='-')f=-1;
    ch=getchar();
  }
  while(ch>='0'&&ch<='9')
  {
    x=x*10+ch-'0';
    ch=getchar();
  }
  return x*f;
}
int main()
{
  int n=read()//这就是读入了n（注意只能用来读入int类型的数据，long long还需更改）
  system("pause");
  return 0;
}

Read函数使用例子

#include <iostream> // std::cout
#include <fstream> // std::ifstream

int main () {

std::ifstream is ("test.txt", std::ifstream::binary);
if (is) {
// get length of file:
is.seekg (0, is.end);
int length = is.tellg();
is.seekg (0, is.beg);

char * buffer = new char [length];

std::cout << "Reading " << length << " characters... ";
// read data as a block:
is.read (buffer,length);

if (is)
std::cout << "all characters read successfully.";
else
std::cout << "error: only " << is.gcount() << " could be read";
is.close();

// ...buffer contains the entire file...

delete[] buffer;
}
return 0;
}