C++常用I/O流技术

最新推荐文章于 2025-11-25 10:31:53 发布

转载最新推荐文章于 2025-11-25 10:31:53 发布 · 921 阅读

文章标签：

#c++ #iostream #ios #system #whitespace #hex

本文介绍了C++中如何使用格式控制进行数据输出，包括左对齐、右对齐、精度控制等，并展示了如何读写文件，包括单个字符和结构体对象的文件操作。

//格式控制

#include<iostream>
//format manipulator.
#include<iomanip>
//
#include<cstdlib>
using namespace std;
int main()
{   //Function Object.
cout << setw(20) << "hello" << endl;
cout << left << setw(10) << "hello" << endl;
cout << setprecision(4) << 2008.852 << endl;
cout << right << setw(20) << setfill("*") << "oh,mygod" << endl;

cout << scientific << uppercase << 300.89 << endl;
cout << scientific << nouppercase << 300.89 << endl;
cout << fixed << 300.89 << endl;

cout << showbase << oct << 9 << endl;
cout << showbase << dec << showpos << 100 << endl;
cout << noshowpos << 100 << endl;
cout << hex << 100 << endl;

cout << boolalpha << true << endl;
cout << noboolalpha << true << endl;

//show weight
//cout << hex << 100 << endl;
cout << showbase << 458 << endl;
//解除设置的格式
cout.unsetf(ios::hex);
cout << showbase << 458 << endl;

//show point
cout << showpoint << 152 << endl;
//
system("pause");
return 0;
}

//多个字符的读写

#include<cstdlib>
#include<iostream>
#include<fstream>
using namespace std;
//
typedef struct {
char name[10];
int age;
}Student;
//
int main()
{
Student s;
strcpy(s.name, "rushgk");
s.age = 23;
//
ofstream out("c:/Student.txt",ios::out);
//write
out.write(reinterpret_cast<char*>(&s), sizeof(Student));
//
out.close();
//read
ifstream in("c:/Student.txt", ios::in);
//
in.read(reinterpret_cast<char*>(&s), sizeof(Student));
//
cout << s.name << " " << s.age << endl;
system("pause");
return 0;
}

//单个字符的读写

//读出get() 写入 put()
#include<cstdlib>
#include<iostream>
#include<fstream>
using namespace std;

int main()
{
ifstream testFile;
testFile.open("c:/wFileTest.txt", ios::in | ios::binary);
if(!testFile)
{
  cout << "打开文件失败!" << endl;
  system("pause");
  return 1;
}
char c;
//read out by character
while(!testFile.eof())
{
  c = testFile.get();
  cout << c;
}
testFile.close();
system("pause");
return 0;
}
//写入到文件

#include<iostream>
#include<fstream>
using namespace std;
int main()
{

ofstream wFile;
//ios::app (append from...)
wFile.open("c:/wFileTest.txt", ios::out  | ios::app);
//ios::trunc (cover original before writing data...)
// wFile.open("c:/wFileTest.txt", ios::out | ios::trunc);
if(!wFile)
{
  cout << "file open failure " << endl;
  return 1;
}
wFile << "apple" << " " <<"苹果" << endl;
wFile << "water" << " " <<"水" << endl;
wFile << "fuck" << " " << "****" << endl;
wFile.close();

return 0;
}
//读出到文件

#include<iostream>
#include<fstream>
#include<cstdlib>
using namespace std;

int main()
{
ifstream rFile;
rFile.open("c:/wFileTest.txt", ios::in);
if(!rFile)
{
  cout << " open file failure " << endl;
  system("pause");
  return 1;
}
char one[10], two[10];
//Read fILE
/** Key words: whiteSpace
  *          overloaded >> and <<
  **/
rFile >> one >> two;
cout << one << " " << two << endl;
//Auto
rFile >> one >> two;
cout << one << " " << two << endl;
//Auto
rFile >> one >> two;
cout << one << " " << two << endl;
rFile.close();
system("pause");
return 0;
}

//还有两个函数seekg() & seekp() 用于任意制定文件指针的位置然后读写，google下