seekp()和seekg()函数简单的应用

来源：互联网发布：js移除数组中某个元素编辑：程序博客网时间：2024/06/01 12:11

#include<iostream>
#include<fstream>
using namespace std;
class Stu
{
public:
char name[10];
int id;
Stu()
{
  strcpy_s(name, "Z");
  id = 0;
}
Stu(char *n, int i)
{
  strcpy_s(name, n);
  id = i;
}
};
int main()
{
ofstream out1;
out1.open("d.dat", ios::binary);
Stu s1[3];
s1[0] = { "A", 10 };
s1[1] = { "B", 20 };
s1[2] = { "C", 30 };

for (int i = 0; i < 3; i++)
{
out1.write((char*)&s1[i], sizeof(s1[i]));//保存到磁盘中
}
out1.close();
out1.open("d.dat", ios::binary);
out1.seekp(2 * sizeof(s1[0]), ios::cur);//将磁盘文件指针设置到s1[2]的位置
Stu ss("lin", 20);
out1.write((char*)&ss, sizeof(ss));//修改s1[2]的值

out1.close();

ifstream in1;
Stu p;
in1.open("d.dat", ios::binary);
in1.seekg(2*sizeof(s1[0]), ios::cur);//将文件指针设置到s1[2]的位置
in1.read((char *)&p, sizeof(s1[1]));//读取s1[2]的值，检查修改后是否成功
cout << "name:" << p.name <<'\t'<< "id:" << p.id << endl;
in1.close();
return 0;
}

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