File IO in C++ (text and binary files) part II
In the first C++ programming tutorial on file IO we looked at the theory behind file IO.
In this second C++ programming tutorial on file IO we will look at some examples.
Read and Write characters (text file)
In the example below we will write and read characters from a text file.
We will write a character (given by the user) to a file test.txt as long as the answer to the question “Continue?:” is replayed with y (from yes). If we answer with something else the program must close the test.txt file. The last part of the program will read all characters in the file test.txt.
#include<iostream>
#include<fstream>
using namespace std;
int main(int argc, char *argv[])
{
//code to write characters in a file
char c, ans;
ans='y';
//Open an output stream
ofstream out ("test.txt");
if(out.is_open())
{
//Loop will continue until something other then y is entered
while (ans=='y')
{
cout <<endl << "Continue ?";
cin >> ans;
if(ans=='y')
{
cout << endl << "Enter Character :";
cin >> c;
out.put(c);
}
}
}
out.close();
//code for reading file completely
ifstream in("test.txt");
if(in.is_open())
{
while(!in.eof())
{
c = in.get();
if(!in.eof())
cout << c;
}
}
in.close();
}
Special flags
The table below shows the special flags that can be used to manage files. (These flags are used during opening of the files).
|
ios::app |
Opens the file in append mode |
|
ios::ate |
Opens the file and set the cursor at end of the |
|
ios::binary |
Opens the file in binary mode |
|
ios::in |
Opens the file for reading |
|
ios::out |
Opens the file for writing |
|
ios::trunc |
Opens the file and truncates all the contents from |
Binary copy
In the next example we will copy a binary file to another binary file. We will open two files in binary mode,
one for reading and one for writing.
If both are open then we will copy the content of one file to another.
#include<iostream>
#include<fstream>
using namespace std;
int main(int argc, char *argv[])
{
//Open an input and output stream in binary mode
ifstream in("myimage.jpg",ios::binary);
ofstream out("myimage1.jpg",ios::binary);
if(in.is_open() && out.is_open())
{
while(!in.eof())
{
out.put(in.get());
}
}
//Close both files
in.close();
out.close();
}
Note: of cource you need to supply the myimage.jpg file to copy (or any other jpg file).
Reading and writing an object
In this last example we will write and read an object (student object) to and from a file:
#include<iostream>
#include<fstream>
using namespace std;
class Student
{
char name[20];
int mark;
public:
void GetStudentData();
void ShowStudentData();
};
void Student :: GetStudentData()
{
cout << "Enter Student Name:" << endl;
cin >> name;
cout << "Enter Student Mark:" << endl;
cin >> mark;
}
void Student :: ShowStudentData()
{
cout << "Student Details are:" << endl;
cout << "Name: " << name << endl
<< "Mark: " << mark << endl;
}
int main(int argc, char *argv[])
{
char ans='y';
Student sobj;
//We open student.dat in append mode
ofstream out("student.dat", ios::app);
if(out.is_open())
{
//Loop will continue until something other then y is entered
while( ans == 'y')
{
cout << endl << "Continue ?";
cin >> ans;
if(ans == 'y')
{
sobj.GetStudentData();
out.write((char*) & sobj, sizeof(sobj));
}
}
}
out.close();
ifstream in("student.dat");
if(in.is_open())
{
while(!in.eof())
{
in.read((char*) &sobj, sizeof(sobj));
if(!in.eof())
{
sobj.ShowStudentData();
}
}
}
in.close();
}
As you can see there are many ways to do file IO in the C++ programming language.
That is all for this tutorial.
Tweet This! or use
to share this post with others.
contents are very nice
& unstandable
its simple n understable…gud one
Very nice samples. Thanks in advance.
Thank U !!
It’s really good…. 🙂
i have file contain of 10 personals
no name age tel
1 ghj 33 908777
10
requirement read this data from file and insert and sort using BST in c++