C++ || Class & Input/Output – Display The Contents Of A User Specified Text File To The Screen

April 24, 2012 admin No comments

The following is another intermediate homework assignment which was presented in a C++ programming course. This program was assigned to introduce more practice using the class data structure, which is very similar to the struct data structure.

REQUIRED KNOWLEDGE FOR THIS PROGRAM

Header Files - How To Use Them Class - What Is It? How To Read Data From A File String - Getline Array - Cin.Getline Strcpy - Copy Contents Of An Array #Define

This program first prompts the user to input a file name. After it obtains a file name from the user, it then attempts to display the contents of the user specified file to the output screen. If the file could not be found, an error message appears. If the file is found, the program continues as normal. After the file contents finishes being displayed, a summary indicating the total number of lines which has been read is also shown to the screen.

This program was implemented into 3 different files (two .cpp files, and one header file .h). So the code for this program will be broken up into 3 sections, the main file (.cpp), the header file (.h), and the implementation of the functions within the header file (.cpp).

Note: The data file that is used in this example can be downloaded here.

Also, in order to read in the data .txt file, you need to save the .txt file in the same directory (or folder) as your .cpp file is saved in. If you are using Visual C++, this directory will be located in

Documents > Visual Studio 2010 > Projects > [Your project name] > [Your project name]

======== FILE #1 – Main.cpp ========





		
		
			File #1 - Main.cpp
			
C++
			
			// ============================================================================
// File: Main.cpp 
// ============================================================================
// This program tests the "CFileDisp" object.  It prompts the user for an input
// filename, then attempts to display the contents of that file to stdout.
// After the file contents have been displayed, a summary line indicating the
// total number of lines that have been displayed is written to stdout.
// ============================================================================
#include <iostream>
#include <fstream>
#include "CFileDisp.h"
using namespace std;

// ==== main ==================================================================
//
// ============================================================================

int main()
{
	CFileDisp       myFile;
	char            fname[MAX_LENGTH];
	int             numLines;
	
	// get the filename from the user
	cout << "Enter a filename: ";
	cin.getline(fname, MAX_LENGTH);
	
	// copy the user's filename into the file object
	myFile.SetFilename(fname);
	
	// have the object open the file
	myFile.OpenFile();
	
	// if all is good and well...
	if(myFile.IsValid()==true)
	{
		numLines = myFile.DisplayFileContents();
		
		// close the file
		myFile.CloseFile();
		
		// write how many lines were displayed to stdout
		cout << "nt*** Total lines displayed: " << numLines << endl;
	}
	
	return 0;
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
// File: Main.cpp 
// ============================================================================
// This program tests the "CFileDisp" object.  It prompts the user for an input
// filename, then attempts to display the contents of that file to stdout.
// After the file contents have been displayed, a summary line indicating the
// total number of lines that have been displayed is written to stdout.
// ============================================================================
#include <iostream>
#include <fstream>
#include "CFileDisp.h"
using namespace std;
 
// ==== main ==================================================================
//
// ============================================================================
 
int main()
{
	CFileDisp       myFile;
	char            fname[MAX_LENGTH];
	int             numLines;
	
	// get the filename from the user
	cout << "Enter a filename: ";
	cin.getline(fname, MAX_LENGTH);
	
	// copy the user's filename into the file object
	myFile.SetFilename(fname);
	
	// have the object open the file
	myFile.OpenFile();
	
	// if all is good and well...
	if(myFile.IsValid()==true)
	{
		numLines = myFile.DisplayFileContents();
		
		// close the file
		myFile.CloseFile();
		
		// write how many lines were displayed to stdout
		cout << "nt*** Total lines displayed: " << numLines << endl;
	}
	
	return 0;
}// http://programmingnotes.org/

======== FILE #2 – CFileDisp.h ========

Remember, you need to name the header file the same as the #include from the Main.cpp file. This file contains the function declarations, but no implementation of those functions takes place here.





		
		
			File #2 - CFileDisp.h
			
C++
			
			// ============================================================================
// File: CFileDisp.h
// ============================================================================
// This is the header file which declares the objects which are used to open 
// a text file and display its contents to stdout.
// ============================================================================
#ifndef CFILE_DISP_HEADER
#define CFILE_DISP_HEADER

#include <fstream>
using namespace std;

#define MAX_LENGTH  256

class   CFileDisp
{
public:
	// constructor
	CFileDisp();
	
	// member functions
	void SetFilename(char  newFilename[]);
	/*  Purpose: Copy the user's filename into the file object */
	void OpenFile();
	/* Purpose: Open's the file which is specified by the user */
	bool IsValid();
	/* Purpose: Checks if the file exists. 
	   Post: Returns false if file cannot be found */
	int DisplayFileContents();
	/* Purpose: Display's the file contents to stdout
	   Post: Returns the total number of lines contained in the file */
	void CloseFile();
	/* Purpose: Closes the file */
	
	// destructor
	~CFileDisp();

private:
    bool            m_bIsValid;
    char            m_filename[MAX_LENGTH];
    ifstream        m_inFile;
};
#endif   // CFILE_DISP_HEADER // http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
// File: CFileDisp.h
// ============================================================================
// This is the header file which declares the objects which are used to open 
// a text file and display its contents to stdout.
// ============================================================================
#ifndef CFILE_DISP_HEADER
#define CFILE_DISP_HEADER
 
#include <fstream>
using namespace std;
 
#define MAX_LENGTH  256
 
class   CFileDisp
{
public:
	// constructor
	CFileDisp();
	
	// member functions
	void SetFilename(char  newFilename[]);
	/*  Purpose: Copy the user's filename into the file object */
	void OpenFile();
	/* Purpose: Open's the file which is specified by the user */
	bool IsValid();
	/* Purpose: Checks if the file exists. 
	   Post: Returns false if file cannot be found */
	int DisplayFileContents();
	/* Purpose: Display's the file contents to stdout
	   Post: Returns the total number of lines contained in the file */
	void CloseFile();
	/* Purpose: Closes the file */
	
	// destructor
	~CFileDisp();
 
private:
    bool            m_bIsValid;
    char            m_filename[MAX_LENGTH];
    ifstream        m_inFile;
};
#endif   // CFILE_DISP_HEADER // http://programmingnotes.org/

======== FILE #3 – CFileDisp.cpp ========

This is the function implementation file for the CFileDisp.h class. This file can be named anything you wish as long as you #include “CFileDisp.h”





		
		
			File #3 - CFileDisp.cpp
			
C++
			
			// ============================================================================
// File: CFileDisp.cpp
// ============================================================================
// This file implements the functions which are declared in the CFileDisp
// class, which is located in CFileDisp.h
// ============================================================================
#include <iostream>
#include <cstring>
#include <string>
#include "CFileDisp.h"
using namespace std;

CFileDisp::CFileDisp()
{
	m_bIsValid = 0;
}// end of CFileDisp

void CFileDisp::SetFilename(char  newFilename[])
{
    strcpy(m_filename,newFilename);
}// end of SetFilename

void CFileDisp::OpenFile()
{
	m_inFile.open(m_filename);
}// end of OpenFile

bool CFileDisp::IsValid()
{
	if (m_inFile.fail())
	{
		cout << m_filename << " was not found...nn";
		return false;
	}
	else 
	{
		return true;
	}
}// end of IsValid

int CFileDisp::DisplayFileContents()
{
	int total=0;
	string inLine;
	
	cout << endl;
	
	while(getline(m_inFile, inLine))
	{
		cout << inLine << endl;
		++total;
	}	
	return total;
}// end of DisplayFileContents

void CFileDisp::CloseFile()
{
	m_inFile.close();
}//	end of CloseFile

// this is the destructor
CFileDisp::~CFileDisp()
{
	m_bIsValid = 0;
}// http://programmingnotes.org/
			
				
					
				
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						// ============================================================================
// File: CFileDisp.cpp
// ============================================================================
// This file implements the functions which are declared in the CFileDisp
// class, which is located in CFileDisp.h
// ============================================================================
#include <iostream>
#include <cstring>
#include <string>
#include "CFileDisp.h"
using namespace std;
 
CFileDisp::CFileDisp()
{
	m_bIsValid = 0;
}// end of CFileDisp
 
void CFileDisp::SetFilename(char  newFilename[])
{
    strcpy(m_filename,newFilename);
}// end of SetFilename
 
void CFileDisp::OpenFile()
{
	m_inFile.open(m_filename);
}// end of OpenFile
 
bool CFileDisp::IsValid()
{
	if (m_inFile.fail())
	{
		cout << m_filename << " was not found...nn";
		return false;
	}
	else 
	{
		return true;
	}
}// end of IsValid
 
int CFileDisp::DisplayFileContents()
{
	int total=0;
	string inLine;
	
	cout << endl;
	
	while(getline(m_inFile, inLine))
	{
		cout << inLine << endl;
		++total;
	}	
	return total;
}// end of DisplayFileContents
 
void CFileDisp::CloseFile()
{
	m_inFile.close();
}//	end of CloseFile
 
// this is the destructor
CFileDisp::~CFileDisp()
{
	m_bIsValid = 0;
}// http://programmingnotes.org/

QUICK NOTES:
The highlighted lines are sections of interest to look out for.

The code is heavily commented, so no further insight is necessary. If you have any questions, feel free to leave a comment below.

Once compiled, you should get this as your output





		
		
			Enter a filename: input_file_display_programmingnotes_freeweq_com.txt

346     130     982     90      656     117   595
415     948     126     4       558     571   87
42      360     412     721     463     47    119
441     190     985     214     509     2     571
77      81      681     651     995     93    74
310     9       995     561     92      14    288
466     664     892     8       766     34    639
151     64      98      813     67      834   369

                This is a line of text!

        *** Total lines displayed: 10
			
				
					
				
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						Enter a filename: input_file_display_programmingnotes_freeweq_com.txt
 
346     130     982     90      656     117   595
415     948     126     4       558     571   87
42      360     412     721     463     47    119
441     190     985     214     509     2     571
77      81      681     651     995     93    74
310     9       995     561     92      14    288
466     664     892     8       766     34    639
151     64      98      813     67      834   369
 
                This is a line of text!
 
        *** Total lines displayed: 10

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Posted in: Advanced, C++ Tags: array, c++, char, class, Count, File, functions, if/else, strcmp, Text, text file, While Loop

C++ || Class & Input/Output – Display The Contents Of A User Specified Text File To The Screen

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