09C++文件读取

seekp() 方法用于指定下一个进入输出缓冲区的字符所在的位置。 用于修改缓存区中的值

//指定下一个字符存储的位置
ostream& seekp (streampos pos);
//通过偏移量间接指定下一个字符的存储位置   
ostream& seekp (streamoff off, ios_base::seekdir way);

#include <iostream> //cin 和 cout
#include <fstream>  //文件输入输出流
#include <string.h>
using namespace std;int main()
{//定义一个文件输出流对象ofstream outfile;//打开 ，等待接收数据outfile.open("");const char *str = "/";//将 str 字符串中的字符逐个输出到  文件中，每个字符都会暂时存在输出流缓冲区中for (int i = 0; i < strlen(str); i++){outfile.put(str[i]);//获取当前输出流}cout << "当前位置为：" << llp() << endl;//调整新进入缓冲区字符的存储位置outfile.seekp(23); //等价于：//outfile.seekp(23, ios::beg);//outfile.seekp(-6, ios::cur);//outfile.seekp(-6, ios::end);cout << "新插入位置为:" << llp() << endl;const char *newstr = "python/";outfile.write("python/", 7);//关闭文件之前，刷新 outfile 输出流缓冲区，使所有字符由缓冲区流入文件outfile.flush();outfile.close();system("pause");return 0;
}

4.按字符读取文件

遇到空格会换行

#include <iostream>
#include <fstream> //文件输入输出流
using namespace std;int main(int argc, char const *argv[])
{ifstream infile;infile.open("", ios::in);if (!infile.is_open()){cout << "文件读取失败" << endl;}char buf[1024] = {0};while (infile >>buf) //遇到空格会换行{cout << buf << endl;//输出读取的文本文件数据}infile.close();system("pause");return 0;
}

5.按行读取文件

数组方法，逐行读取，可读取空格

#include <iostream>
#include <fstream> //文件输入输出流
using namespace std;int main(int argc, char const *argv[] )
{ifstream infile;infile.open("", ios::in);if (!infile.is_open()){cout << "读取文件失败" << endl;return -1;}//第二种读取方法char buf[1024];while (line(buf, sizeof(buf))){cout << buf << endl;}infile.close();system("pause");return 0;
}

6.按逐字符读取

#include <iostream>
#include <fstream> //文件输入输出流
using namespace std;int main(int argc, char const *argv[])
{ifstream infile;infile.open("", ios::in);if (!infile.is_open()){cout << "读取文件失败" << endl;return -1;}char c;while ((c &#()) != EOF){cout << c;}cout << endl;infile.close();system("pause");return 0;
}

7.读取至Vector容器中

#include <iostream>
#include <fstream>
#include <string.h>
#include <vector>
using namespace std;int main(int argc, char const *argv[])
{ifstream infile;infile.open("", ios::in);if (!infile.is_open()){cout << "读取文件失败" << endl;return -1;}//第五种读取方法string s;vector<string> v1;while (getline(infile, s)){v1.push_back(s);}for (size_t i = 0; i < v1.size(); i++){cout << v1.at(i);cout << endl;}infile.close();system("pause");return 0;
}

8.写数据到文件

#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;int main(int argc, char const *argv[])
{ofstream outfile;outfile.open("", ios::out | ios::app);if (!outfile.is_open()){cout << "读取文件失败" << endl;return -1;}outfile << "hello world" << endl;outfile << "世界 我来了";outfile.close();system("pause");return 0;
}

ios::noreplace 默认存在

9.二进制读取

#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;int main(int argc, char const *argv[])
{ofstream outfile;outfile.open("", ios::out | ios::binary);if (!outfile.is_open()){cout << "读取文件失败" << endl;return -1;}outfile << "hello world" << endl;outfile << "世界 我来了";outfile.close();system("pause");return 0;
}

1.写入文件

#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;int main(int argc, char const *argv[])
{ofstream outfile;outfile.open("", ios::out | ios::binary);if (!outfile.is_open()){cout << "读取文件失败" << endl;return -1;}string str("Hello, world 张三李四");outfile.write(str.c_str(), sizeof(str));outfile.close();system("pause");return 0;
}

2.读取数据

#include <iostream>
#include <fstream> //文件输入输出流
using namespace std;int main(int argc, char const *argv[] )
{ifstream infile;infile.open("", ios::in|ios::binary);if (!infile.is_open()){cout << "读取文件失败" << endl;return -1;}//第二种读取方法char buf[1024];while (line(buf, sizeof(buf))){cout << buf << endl;}infile.close();system("pause");return 0;
}

stream infile;
infile.open(“”, ios::in|ios::binary);
if (!infile.is_open())
{
cout << “读取文件失败” << endl;
return -1;
}
//第二种读取方法
char buf[1024];
while (line(buf, sizeof(buf)))
{
cout << buf << endl;
}
infile.close();
system(“pause”);
return 0;
}