Lecture# 26 Programming Concepts

1. Lecture# 26 Programming Concepts

2. File Handling

3. Steps to handle file • Open the File • Read / Write the File • Close the File

4. Header File for File Handling • fstream.h • #include <fstream.h> • Input File Stream • ifstream • Output file stream • ofstream

5. Reading File • #include <fstream.h> • ifstream myFile ; • myFile.open ( “File.txt” ) ; c:\myProg\File.txt • myFile.close();

6. My.txt myfile My.txt myfile Process: close myfile.open ( “My.txt” ,ios::in) ; Process: open myfile.close ( “My.txt” ) ;

7. ifstream myFile; • myFile.open("File.txt“,ios::in); • if(!myFile){ • cout<<"The file cannot open"; • return 0; • } • char a; • myFile>>a; • cout<<a; • myFile.close();

8. void main(){ int x; cin>>x; cout<<x; ifstream hFile; hFile.open(“File.txt”,ios::in); char a; hFile>>a; cout<<a; getch() } >> << 9 T >> This is a File.txt

9. ifstream myFile; • myFile.open("File.txt"); • if(!myFile){ • cout<<"The file cannot open"; • return 0; • } • char a[10]; • myFile>>a; • cout<<a; • myFile.close();

10. myfile.eof ( ) • while ( !myfile.eof ( ) ) • { • myfile >> varName ; • cout<<varName; • }

11. get() • while ( !myFile.eof ( ) ) • { • myFile.get ( ch ) ; • cout << ch ; • }

12. Generic Syntax • fstream Myfile • Myfile.open( “File.txt” , mode ) ; // Generic syntax ifstream • Myfile.open ( “File.txt” , ios :: in ) ; OR • Myfile.open ( “File.txt” , ios :: out ) ;

13. Read \ Write • ifstream myInputFile ( “myfile.txt” , ios :: in ) ; • ofstream myOutputFile ( “myfile.txt” , ios :: out ) ;

14. Output File Modes • Create a new file • Overwrite an existing file • Append some text • Randomly accessing a file

15. #include<fstream> • void main(){ • ofstream myFile("File.txt",ios::out); • if ( !myFile ) // Error check • { • cout << "Your file could not be opened"; • } • int i=0; • char a[100];

16. gets(a); • while(a[i]!='\0'){ • myFile<<a[i]; • i++; • } • myFile.close ( ) ; • getch(); • }

17. Example

18. #include<fstream> • #include<stdlib> • int main(){ • ifstream hFile("File.txt",ios::in); • if(!hFile){ • cerr<<"File cannot open"; • getch(); • exit(1); • }

19. int account; • char name[30]; • float balance; • cout<<"Account\t"<<"Name\t"<<"Balance\n"; • while(!hFile.eof()){ • hFile>>account>>name>>balance; • cout<<account<<"\t"<<name<<"\t"<<balance<<endl; • } • getch(); • return 0; • }

20. while( hFile>>account>>name>>balance){ • cout<<account<<"\t"<<name<<"\t"<<balance<<endl; • }

21. File opening Modes • ios :: in open for reading (default for ifstream) • ios :: out • open for writing (default for ofstream) • ios :: app start writing at end of file (APPend) • ios :: ate start reading or writing at EOF of file (ATEnd) • ios :: trunc truncate file to zero length if it exists (TRUNCate)

22. File opening Modes • ios :: nocreate error when opening if file does not already exist • ios :: noreplace error when opening for output if file already exists • ios :: binary open file in binary (not text) mode

23. Problems • Copy the contents of one text file on the other text file. • Copy the contents of one text file at the end of other text file

24. Opening any File • #include<iostream.h> • #include<conio.h> • #include<fstream.h> • #include<stdio.h> • int main(){ • clrscr(); • fstream myFile; • char name[10]; • cout<<"Enter the name of file want to Open:"; • gets(name); • myFile.open(name,ios::in);

25. if(!myFile){ • cout<<"The file cannot open:"; • getch(); • return 0; • } • char a; • while(!myFile.eof()){ • myFile.get(a); • cout<<a; • } • myFile.close(); • getch(); • return 0; • }

26. #include<iostream.h> • #include<conio.h> • #include<fstream.h> • #include<stdio.h> • int main(){ • clrscr(); • fstream myFile1,myFile; • char name[10],name1[10]; • cout<<"Enter the name of file want to copy:"; • gets(name); • myFile.open(name,ios::in); • cout<<"\nEnter the name of file where u want to paste:"; • gets(name1); • myFile1.open(name1,ios::out);

27. if(!myFile){ • cout<<"The file cannot open:"; • getch(); • return 0; • } • char a; • while(!myFile.eof()){ • myFile.get(a); • myFile1.put(a); • } • myFile.close(); • myFile1.close(); • getch(); • return 0; • }