File Handling – C++

A small Example on File Handling.

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Example :

#include<fstream.h>

#include<string.h>

#include <stdio.h>

  class File

      {

           private:

              char empnm[20];

              float sal;

           public:

              void Append();

              void Print();

              void Modify();

              void Del();

      };

  void File::Append()

      {

           File F;

           fstream fptr;

           fptr.open("emp.dat",ios::app);

           cout<<"\n\tEnter Employee Name : ";

           cin.ignore();

           cin.get(F.empnm,20);

           cout<<"\n\tEnter Employee Salary : ";

           cin>>F.sal;

           fptr.write((char *)&F,sizeof(F));

           fptr.close();

      }

  void File::Print()

      {

           File F;

           fstream fptr;

           fptr.open("emp.dat",ios::in);

           while(fptr.read((char *)&F,sizeof(F)))

              {

                   cout<<"\n\tEmployee Name : "<<F.empnm;

                   cout<<"\n\tEmployee Salary : "<<F.sal<<"\n";

              }

           fptr.close();

      }

  void File::Modify()

      {

      long pos;

      File F;

      char name[20];

      fstream fptr;

      fptr.open("emp.dat",ios::out|ios::in);

      cout<<"\n\tEnter Name to Delete : ";

      cin.ignore();

      cin.get(name,20);

      while(fptr.read((char *)&F,sizeof(F)))

           {

              if(strcmpi(name,F.empnm)==0)

                   {

                        cout<<"\n\tEnter New Salary : ";

                        cin>>F.sal;

                        pos=fptr.tellg();

                        cout<<pos<<"\n";

                        fptr.seekg(pos-sizeof(F));

                        fptr.write((char *)&F,sizeof(F));

                   }

           }

      fptr.close();

  }

  void File::Del()

      {

           long pos;

           File F;

           char name[20];

           fstream fptr,fptr1;

           fptr.open("emp.dat",ios::in);

           fptr1.open("temp.dat",ios::out);

           cout<<"\n\tEnter Name to Delete : ";

           cin.ignore();

           cin.get(name,20);

           while(fptr.read((char *)&F,sizeof(F)))

              {  if(strcmpi(name,F.empnm)!=0)

                        {

                              fptr1.write((char *)&F,sizeof(F));

                        }

              }

           fptr.close();

           fptr1.close();

           remove("emp.dat");

           rename("temp.dat","emp.dat");

      }

  int main()

      {

           File f;

           int ch=0;

           while(ch!=5)

              {

                   cout<<"\n\t1. Append";

                   cout<<"\n\t2. Print";

                   cout<<"\n\t3. Modify";

                   cout<<"\n\t4. Delete";

                   cout<<"\n\t5. Exit";

                   cout<<"\n\tChoice? ";

                   cin>>ch;

                   switch(ch)

                        {

                            case 1: f.Append();break;

                            case 2: f.Print();break;

                            case 3: f.Modify();break;

                            case 4: f.Del();break;

                            case 5: break;

                        }

              }

           return 0;

      }