Basic file operations in C++ Dr. Ahmed Telba 1

2 Learning Objectives §C++ I/O streams. §Reading and writing sequential files. §Reading and writing random access files.

3 Table 12-1

4 Figure 1-1

5 Figure 1-2

6 C++ Files and Streams §Why use File Handling §For permanent storage. §The transfer of input - data or output - data from one computer to another can be easily done by using files. §For read and write from a file you need another standard C++ library called fstream, which defines three new data types:

7 DatatypeDescription ofstreamThis is used to create a file and write data on files ifstreamThis is used to read data from files fstreamThis is used to both read and write data from/to files

How to achieve File Handling  For achieving file handling in C++ we need follow following steps Naming a file Opening a file Reading data from file Writing data into file Closing a file 8

Functions use in File Handling FunctionOperation open()To create a file close()To close an existing file get()Read a single character from a file put()write a single character in file. read()Read data from file write()Write data into file. 9

10 Closing a File A file must be close after completion of all operation related to file. For closing file we need close() function. Syntax outfile.close(); Defining and Opening a File The function open() can be used to open multiple files that use the same stream object. Syntax file-stream-class stream-object; stream-object.open("filename"); Example ofstream outfile; // create stream outfile. open ("data1"); // connect stream to data1

File Opening mode ModeMeaningPurpose ios :: outWriteOpen the file for write only. ios :: inreadOpen the file for read only. ios :: appAppendingOpen the file for appending data to end-of-file. ios :: ateAppendingtake us to the end of the file when it is opened. 11 Example fstream file; file.Open("data. txt", ios :: out | ios :: in);

FLAGES IN FILE §FLAGES IN FILE 12

13 File Open Modes ios:: app - (append) write all output to the end of file ios:: ate - data can be written anywhere in the file ios:: binary - read/write data in binary format ios:: in - (input) open a file for input ios::out - (output) open afile for output ios: trunc -(truncate) discard the files’ contents if it exists

What is a File? §A file is a collection on information, usually stored on a computer’s disk. Information can be saved to files and then later reused.

File Names §All files are assigned a name that is used for identification purposes by the operating system and the user.

16 Setting Up a Program for File Input / Output §Before file I/O can be performed, a C++ program must be set up properly. §File access requires the inclusion of § # include

Input &Output with files §Input / Output with files §C++ provides the following classes to perform output and input of characters to/from files: §ofstream: Stream class to write on files §ifstream: Stream class to read from files §fstream: Stream class to both read and write from/to files. 17

18 Path of file §Before data can be written to or read from a file, the file must be opened. ifstream inputFile; inputFile.open(“customer.dat”); // Path of file using : ifstream fin("D:\\data.txt ");

§// basic file operations §#include §using namespace std; §int main () { § ofstream myfile; § myfile.open ("example.txt"); § myfile << "Writing this to a file.\n"; § myfile.close(); §return 0; §} 19

Writing to file §#include §using namespace std; §int main() §{ §char x = 's'; §int d = 77; §double i = 3.14; § ofstream fout("data.txt"); §fout << x << d << ' ' << i ; §fout.close(); § §cout << "File Completed\n"; §return 0; §} 20

§#include §using namespace std; §int main() § { §ofstream fout; § fout.open("FF.txt"); § fout << "HELLOW FILE.\n"<< "WELCOME YOU PROGRAM\n" §<< "WHAT DA YOU LIKE OF ME\n"; § fout.close(); §} 21

§// writing in file §#include //divide by 7 §#include §using namespace std; § int main() §{ §ofstream fout("data.txt"); §for(int i=4;i<=200;i++) §{ §if(i%7==0) §fout<<i<<" : divide by Two (7)."<<"\n"; §} §fout.close(); §} 22

§#include // !x=x*(x-1)*(x-2)…. §#include §using namespace std; §int main() §{ §ofstream fout("factial.txt"); § // Variable Declaration § int counter, n, fact = 1; § // Get Input Value § cout<<"Enter the Number :"; § cin>>n; § //for Loop Block § for (int counter = 1; counter <= n; counter++) § { § fact = fact * counter; § } § fout<<n<<" Factorial Value Is "<<fact; § fout.close(); §cout<<n<<" Factorial Value Is "<<fact; § return 0; § } 23

24 Testing for Open Errors dataFile.open(“cust.txt”, ios::in); if (!dataFile) { cout << “Error opening file.\n”; }

25 Another way to Test for Open Errors dataFile.open(“cust.dat”, ios::in); if (dataFile.fail()) { cout << “Error opening file.\n”; }

// writing on a text file §// writing on a text file §#include §using namespace std; §int main () { § ofstream myfile ("examplett.dat"); § if (myfile.is_open()) § { § myfile << "This is a new file created in cpp.\n"; § myfile << "This is another line.\n"; § myfile.close(); § } § else cout << "Unable to open file"; §return 0; §} 26

file operations in C++ §#include § using namespace std; §int main () § { ofstream myfile; § myfile.open ("example22.txt"); § myfile << "Writing this to a file.\n"; § myfile<<"Hope fine”" << endl; §myfile<<"this frist file ”" << endl; § myfile.close(); §return 0; } 27

§#include §using namespace std; §int main() §{ char FirstName[30], LastName[30]; § int Age; § char FileName[20]; § cout << "Enter First Name: "; § cin >> FirstName; § cout << "Enter Last Name: "; § cin >> LastName; § cout << "Enter Age: "; § cin >> Age; § cout << "\nEnter the name of the file you want to create:..txt "; § cin >> FileName; § ofstream Students(FileName, ios::out); § Students << FirstName << "\n" << LastName << "\n" << Age; § cout << "\n\n"; § return 0; §} 28

Write to file §#include §using namespace std; §int main() § { ofstream fout; § fout.open("FFFF.txt"); § fout << "Asalamualikom hope fine.\n" §<< "WELCOME TO GE 211 FILE SECTION PROGRAM\n" §<< "HOPE TO DO WELL IN SECOND MEDTERM EXAM\n"; § fout.close(); §} 29

§//Write the odd number in file §#include §using namespace std; §int main() § { ofstream fout; § fout.open("E:\\firsteee.txt"); §int i,j; §for(i=2;i<30;i+=2) §{ §fout<<i<<"\t"; §cout<<i<<"\t";} § fout.close(); §} 30

§// print in file Even number 1:30 §#include §using namespace std; §int main() § { ofstream fout; § fout.open("D:\\firstExa.txt"); §int i,j; §for(i=1;i<30;i+=2) §fout<<i<<"\t"; § fout.close(); §} 31

§#include §using namespace std; §int main() §{ofstream fout; § fout.open("D:\\ffffff.txt"); §float i,j,m,sum; §j=3; §sum=0; §for(i=1;i<=100;i++){ §m=(i*i)/(j*j); §j=j+2; §sum=sum+m;} §cout<<"seque="<<sum<<endl; §fout<<"seque="<<sum<<endl; §fout.close(); § } 32

§//write equation for this series §#include §using namespace std; § int main() §{ § int i,j,m,n,sum; §sum=0; §cin>>n; §for(i=1 ;i<=n ;i++) §{ §m=i*i; §sum=sum+m; } §cout<< "seque="<<sum<< endl; §} 33

§#include // using both file and screen §#include §using namespace std; § int main() §{ § ofstream fout; § fout.open("xxxx.txt"); § int i,j,m,n,sum; §sum=0; §cout<<"equation for this series ="<<endl; §cin>>n; §for(i=1 ;i<=n ;i++) §{ §m=i*i; §sum=sum+m; } §cout<< "seque="<<sum<< endl; §fout<< "seque= written in file is="<<sum<< endl; §fout.close(); §} 34

§#include §using namespace std; § int main() §{ §float i,m,n,b,a,y,x,s; §y=0; §b=2; §cout<<"enter the last power of\n"; §cin>>n; §cout<<"enter the volue of(x)\n"; §cin>>s; §for(i=1;i<=n;i++){ §x=pow(s,i); §a=pow(b,i); §m=x/a; §y=y+m; § } §cout<<"y= "<<y; §} 35

§#include §using namespace std; §main() §{ofstream fout; § fout.open("D:\\UUUU.txt"); §float i,m,n,b,a,y,x,s; §y=0; §b=2; §cout<<"enter the last power of\n"; §cin>>n; §cout<<"enter the volue of(x)\n"; §cin>>s; §for(i=1;i<=n;i++){ §x=pow(s,i); §a=pow(b,i); §m=x/a; §y=y+m; § } §cout<<"y= "<<y; §fout<<"y= "<<y; §fout.close(); §} 36

§//Fenonci seris §#include §using namespace std; §main() §{ofstream fout; § fout.open("D:\\finoncy.txt"); §int i,s,b,d ; §s=0; §d=1; §for(i=0;i<20;i++) §{ §b=s; §s=d; §d=s+b; §fout<<d<<"\t"; §} §fout.close(); § } 37

§//write to file §#include §using namespace std; § int main() §{ § ofstream fout; § fout.open("D:\\Seris.txt"); § int i,j,m,n,sum; §sum=0; §cin>>n; §for(i=1 ;i<=n ;i++) §{ §m=i*i; §sum=sum+m; } §fout<< "seque="<<sum<< endl; §fout.close(); §} 38

Read from file §#include §using namespace std; § int main() § { char array [80]; § ifstream fin; § fin.open("firstExa.txt"); § while(!fin.eof()) § {fin.getline(array,80); § cout<<array<<endl;} § fin.close(); §} 39

Write in binary file § ofstream fout ; § fout.open("file path",iostream family § fout.write((char*)& data,sizeo(data); 40

Binary form §#include §main() §{ int Array[80],i; § for(i=0;i<10;i++) § cin>> Array[i]; § ofstream fout; § fout.open("D:\\ahmed.bin",ios::binary); § fout.write((char *) & Array, sizeof(Array)); § fout.close(); § system("pause"); § } 41

§// writing on a text file §#include §using namespace std; §int main () { § ofstream myfile ("example.txt"); § if (myfile.is_open()) § { § myfile << "This is a line.\n"; § myfile << "This is another line.\n"; § myfile.close(); § } § else cout << "Unable to open file"; §return 0; §} Slide 6- 42

§// reading a text file §#include §using namespace std; §int main () { § string line; § ifstream myfile ("example.txt"); § if (myfile.is_open()) § { § while ( myfile.good() ) § { § getline (myfile,line); § cout << line << endl; § } § myfile.close(); § } § else cout << "Unable to open file"; §return 0; §} Slide 6- 43

Using fout Slide §#include §using namespace std; §int main (int aaa,char *avg[]) §{ §ofstream fout ("my_out.txt"); §fout<<" Assalamualikom Hope fine" << endl; §fout<<"Please tray good in second exam this frist file " << endl; §return 0;}

Write in file §#include §using namespace std; §int main( ) §{ §//cout<<"Exam1\n"; § // ifstream ;// read § // ofstream ;// write § // fstream;//read &write §ofstream myfile; §myfile.open("kkkk.txt"); §myfile<< "Exam1 is ok\n"; §myfile<< "please tray good in second exam"; §myfile.close(); §return 0; §} 45

Using app §#include §using namespace std; §int main( ) §{ §/*cout<<"Exam1\n"; § ifstream ;// read § ofstream ;// write § fstream;//read &write*/ §fstream myfile; §myfile.open("kkkk.txt",ios ::out|ios::app); §//myfile<< "Exam1 is ok\n"; §myfile<< "please tray good in second exam****************\n"; §//cout<<myfile.rdbuf(); §myfile.close(); §return 0; §} 46

Read from file §#include §using namespace std; §int main( ) §{ §/*cout<<"Exam1\n"; § ifstream ;// read § ofstream ;// write § fstream;//read &write*/ §ifstream myfile; §myfile.open("kkkk.txt"); §//myfile<< "Exam1 is ok\n"; §//myfile<< "please tray good in second exam"; §cout<<myfile.rdbuf(); §myfile.close(); §system("pause"); § return 0; §} 47

Input &Output with files §Input / Output with files §C++ provides the following classes to perform output and input of characters to/from files: §ofstream: Stream class to write on files §ifstream: Stream class to read from files §fstream: Stream class to both read and write from/to files. 48

Reading from file §#include §using namespace std; §int main() §{ §char m; §int i; §double j; §ifstream fin("data.txt"); §fin >> m >> i >> j; §cout << m << endl §<< i << endl §<< j << endl ; §fin.close();} 49

§// basic file operations §#include §using namespace std; §int main () { § ofstream myfile; § myfile.open ("example.txt"); § myfile << "Writing this to a file.\n"; § myfile.close(); § return 0; §} 50

classdefault mode parameter ofstreamios::out ifstreamios::in fstreamios::in | ios::out ofstream myfile; myfile.open ("example.bin", ios::out | ios::app | ios::binary); 51

Basic file operations §// basic file operations §#include §//#include §using namespace std; §int main () { § ofstream myfile; § myfile.open ("XXX.txt"); § myfile << "**Writing this to a file.\n"; § myfile << "****Writing this to a file.\n"; § myfile << "*********Writing this to a file.\n"; § myfile.close(); § system("PAUSE"); § return 0; §} 52

Basic file operations §#include §using namespace std; §int main (int argc, char *arvg[ ]) §{ § ofstream fout("XXX.txt"); § fout << "**Writing this to a file.\n"; § fout << "****Writing this to a file.\n"; § fout << "*********Writing this to a file.\n"; §system("PAUSE"); § return EXIT_SUCCESS; §} 53

FILE IN C++ ios::inOpen for input operations. ios::outOpen for output operations. ios::binaryOpen in binary mode. ios::ate Set the initial position at the end of the file. If this flag is not set to any value, the initial position is the beginning of the file. ios::app All output operations are performed at the end of the file, appending the content to the current content of the file. This flag can only be used in streams open for output-only operations. ios::trunc If the file opened for output operations already existed before, its previous content is deleted and replaced by the new one. 54

§// reading a text file §#include §using namespace std; §int main () { §char buffer[256]; §ifstream examplefile ("examplepp.txt"); §if (! examplefile.is_open()) §{ cout << "Error opening file"; exit (1); } §while (! examplefile.eof() ) §{ §examplefile.getline (buffer,100); §cout << buffer << endl; §} §return 0; §} 55

§// writing on a text file §#include §using namespace std; §int main () { § ofstream myfile ("example.txt"); § if (myfile.is_open()) § { § myfile << "This is a line.\n"; § myfile << "This is another line.\n"; § myfile.close(); § } § else cout << "Unable to open file"; § return 0; §} 56