5.1 text documents

5.1.1 writing documents

The steps for writing files are as follows:

1. Include header file

   #include <fstream>

2. Create flow object

   ofstream ofs;

3. Open file

   ofs.open("file path", opening method);

4. Write data

   Ofs < < "written data";

5. Close file

   ofs.close();

File opening method:

Open mode	explain
ios::in	Open file for reading
ios::out	Open file for writing
ios::ate	Initial location: end of file
ios::app	Write file in append mode
ios::trunc	If the file exists, delete it before creating it
ios::binary	Binary mode

Note: the file opening method can be used in conjunction with the | operator

For example, write the file IOS:: binary | IOS:: out in binary mode

Example:

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

// Text file write file

void test01()
{
	// 1. Include header file fstream
	
	// 2. Create flow object

	ofstream ofs;

	// 3. Specify how to open
	ofs.open("test.txt", ios::out);

	// 4. Write content
	ofs << "Name: Zhang San" << endl;
	ofs << "Gender: Male" << endl;
	ofs << "Age: 18" << endl;

	// 5. Close file
	ofs.close();
}

int main()
{


	system("pause");

	return 0;
}

Summary:

• The file operation must contain the header file fstream
• You can use ofstream or fsstream class to read files
• When opening a file, you need to specify the path of the operation file and the opening method
• Use < < to write data to a file
• After the operation, close the file

5.1.2 document reading

Reading a file is similar to writing a file, but there are many ways to read it

The steps for reading files are as follows:

1. Include header file

   #include <fstream>

2. Create flow object

   ifstream ifs;

3. Open the file and judge whether the file is opened successfully

   ifs.open("file path", opening method);

4. Read data

   Four ways to read

5. Close file

   ifs.close();

Example:

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


// Text file read file
void test01()
{
	// 1. Include header file

	// 2. Create flow object
	ifstream ifs;

	// 3. Open the file and judge whether it is opened successfully
	ifs.open("test.txt", ios::in);

	if (!ifs.is_open())
	{
		cout << "File open failed" << endl;
		return;
	}

	// 4. Read data

	// First kind
	//char buf[1024] = { 0 };
	//while ( ifs >> buf )
	//{
	//	cout << buf << endl;
	//}

	// Second
	//char buf[1024] = { 0 };
	//while ( ifs.getline(buf, sizeof(buf)) )
	//{
	//	cout << buf << endl;
	//}

	// Third
	//string buf;
	//while ( getline(ifs, buf) )
	//{
	//	cout << buf << endl;
	//}

	// Fourth
	//char c;
	//while ( (c = ifs.get()) != EOF ) // EOF  end of file
	//{
	//	cout << c;	
	//}

	// 5. Close file
	ifs.close();
}

int main()
{

	test01();


	system("pause");

	return 0;
}

Summary:

• I fstream or fsstream class can be used to read files
• Using is_ The open function can judge whether the file is opened successfully
• Close close file

5.2 binary files

Read and write files in binary mode

The opening method should be specified as ios::binary

5.2.1 writing documents

Binary file writing mainly uses the stream object to call the member function write

Function prototype: ostream & write (const char * buffer, int len);

Parameter explanation: the character pointer buffer points to a storage space in memory. len is the number of bytes read and written

Example:

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

class Person
{
public:

	char m_Name[64]; // full name
	int m_Age; // Age
};

void test01()
{
	// 1. Include header file

	// 2. Create flow object
	ofstream ofs("Person.txt", ios::out | ios::binary);

	// 3. Open file
	// ofs.open("Person.txt", ios::out | ios::binary);


	// 4. Write file
	Person p = { "Zhang San", 18 };
	ofs.write((const char*)&p, sizeof(Person));

	// 5. Close file
	ofs.close();
}

int main()
{

	test01();

	system("pause");

	return 0;
}

Summary:

• The file output stream object can write data in binary mode through the write function

5.2.2 document reading

Binary file reading mainly uses the stream object to call the member function read

Function prototype: istream & read (char * buffer, int len);

Parameter explanation: the character pointer buffer points to a storage space in memory. len is the number of bytes read and written

Example:

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

class Person
{
public:

	char m_Name[64]; // full name
	int m_Age; // Age
};

// Binary file read file
void test01()
{
	// 1. Include header file

	// 2. Create flow object
	fstream ifs;

	// 3. Open the file to judge whether the file is opened successfully
	ifs.open("Person.txt", ios::in | ios::binary);
	
	if (!ifs.is_open())
	{
		cout << "File open failed" << endl;
		return;
	}

	// 4. Read file
	Person p;
	
	ifs.read((char*)&p, sizeof(Person));

	cout << "full name:" << p.m_Name << endl;

	cout << "Age:" << p.m_Age << endl;


	// 5. Close file
	ifs.close();
}

int main()
{

	test01();

	system("pause");

	return 0;
}

• The file input stream object can read data in binary mode through the read function