How to use a text files as a sql fields to edit,delete and modify records using c++

[vinoth66]

i want to search and display the field stored in text file and also i want to delete the field that is entered. help me with this code. case 3 and 4 is incomplete.

#include<iostream>
#include<fstream>
#include<string>
using namespace std;
int main()
{
    int a;
    int st_id;
    string st_name,st_place,ch;
    ofstream ofile;
    ifstream nfile;
    do
    {
        cout<<"\n1.Insertion";
        cout<<"\n2.Display";
        cout<<"\n3.Delete";
        cout<<"\n4.Search";
        cout<<"\n Press 0 to exit";
        cout<<"\nEnter your choice\t";
        cin>>a;
        switch(a)
        {
        case 1:
            ofile.open("student.txt",ios::out | ios::app | ios::binary);
 
            if(ofile.is_open())
            {
                cout<<"\nEnter the Student Id: ";
                cin>>st_id;
                cout<<"\nEnter the name of the student: ";
                cin>>st_name;
                cout<<"\nEnter the location of student: ";
                cin>>st_place;
                long begin,end;
                ifstream myfile ("student.txt");
                begin = myfile.tellg();
                myfile.seekg (0, ios::end);
                end = myfile.tellg();
                myfile.close();
                if((end-begin)==0)
                {
                    ofile<<"\nstudent id\t"<<"student name\t"<<"location\n";
                }
                ofile<<"\n"<<st_id<<"\t\t"<<st_name<<"\t\t"<<st_place<<"\n";
                ofile.close();
            }
            else
                cout<<"failed to Insert values into file";
            break;
        case 2:
            nfile.open("student.txt",ios::in);
            if(nfile.is_open())
            {
 
                getline(nfile,ch);
                cout<<ch<<" inside print   "<<endl;
                nfile.close();
            }
            else
                cout<<"failed to get values";
            break;
        case 3:
            ofile.open("student.txt",ios::binary|ios::in);
            if(ofile.is_open())
            {
                int num,choice;
                string plo;
                cout<<"\nEnter your choice to remove";
                cout<<"\nTo delete elements by ID press 1";
                cout<<"\nTo delete elements by location or name press 2\n";
                cin>>choice;
                switch(choice)
                {
                case 1:
                    cout<<"\nEnter the id remove:";
                    cin>>num;
                    if(num==st_id)
                    {
 
                        cout<<"removed";
                    }
                    else
                        cout<<"\nId not found";
                    break;
 
                case 2:
                    cout<<"\nEnter the name or location of the student:";
                    cin>>plo;
                    if(plo==st_name)
                    {
                        cout<<"removed";
                    }
                    else if(plo==st_place)
                    {
                        cout<<"removed";
                    }
                    else
                        cout<<"\n content is not found";
                    break;
                }
 
 
            }
            break;
        case 4:
            ofile.open("student.txt",ios::binary|ios::in);
            if(ofile.is_open())
            {
                int sid,option;
                string spn;
                cout<<"\nchoose your option for search";
                cout<<"\nTo search elements by ID press 1";
                cout<<"\nTo search elements by location or name press 2\n";
                cin>>option;
                switch(option)
                {
                case 1:
                    cout<<"\nEnter the id for search:";
                    cin>>sid;
                    if(sid==st_id)
                    {
 
                        cout<<st_id<<"\t"<<st_name<<"\t"<<st_place;
                        cout<<"content";
                    }
                    else
                        cout<<"\nId not found";
                    break;
 
                case 2:
                    cout<<"\nEnter the name or location of the student:";
                    cin>>spn;
                    if(spn==st_name)
                    {
                        cout<<st_id<<"\t"<<st_name<<"\t"<<st_place;
                        cout<<"content";
                    }
                    else if(spn==st_place)
                    {
                        cout<<st_id<<"\t"<<st_name<<"\t"<<st_place;
                        cout<<"content";
                    }
                    else
                        cout<<"\n content is not found";
                    break;
                }
 
 
            }
            break;
        }
    }while(a!=0);
    return 0;
}

thanks for the lookup and suggestion

[weaknessforcats]

I believe you are writing the program too soon. Put this aside and start a new project. In this project you will have functions to manage a database. In this case a text file. The function should return a FILE* to the file it created.

Write a function to create the database by creating the file.

Now write the main(), call this function and verify the database is created. I recommend you not use binary as a beginner.

Now write a function to add a student. I recommend a struct here with a member for student ID, a string for student name and a string for student location.

bool write(FILE* pf, string id, string name, string loc);
 

The function to add the student must be sure the record layout is exactly correct. Let's assume your record layout is:

1 - 8 student id
9-38 student name
39-50 student location.

The add function UNPACKS the struct puts the student id in an 8 byte array, outs the student name in a 30 byte array and puts the student location in an 11 byte array. It then writes the three arrays in the correct order terminated by a \n.

You will need to use string::c_str() to convert the string object into a C style string.

Now test this function in your main().


You should be able to see the contents if your file using notepad or for Linux maybe vi.

Next write a read function that reads a record from the file and returns a struct with the members filled with data from the file.

Next write search functions. One to search for student name, one for location and one for student id. The functions return a FILE* which is positioned to the record searched for. If the data is not found the FILE* returned is zero.

After the search you can call your read to get the data which will be returned in a struct for you. From here you can just display the struct members.

Try to write a function with a FILE* argument rather than doing seek() and tell all over the place. Manage your data using only your database management functions. If there is a problem you can quickly isolate to the file management functions as opposed to starting to debug from main() each time.

Post again and let me know what happened.

[vinoth66]

I tried that too. but while getting input it leaves the field id.and when trying to search and display it prints both the if and else loops

#include <iostream>
#include<fstream>
using namespace std;
class file
{
public:
    char st_id[256],st_name[256],st_place[256];
    string ch;
    void getdata();
    void putdata();
    void display();
    void search();
};
void file::getdata()
{
    ofstream ofile("student.txt",ios::out|ios::app|ios::binary);
    if(ofile.is_open())
    {
        cout<<endl;
        cout<<"\nEnter the Student Id:"<<endl;
        cin.getline(st_id,256);
        cout<<"\nEnter the name of the student:";
        cin.getline(st_name,256);
        cout<<"\nEnter the location of student:";
        cin.getline(st_place,256);
    }
    else
        cout<<"\nFailed to create and Insert";
}
void file::putdata()
{
    ofstream ofile1("student.txt",ios::out|ios::binary|ios::app);
    ifstream nfile("student.text",ios::in);
    long begin,end;
    nfile.open("student.txt");
    begin = nfile.tellg();
    nfile.seekg (0, ios::end);
    end = nfile.tellg();
    nfile.close();
    if((end-begin)==0)
    {
        ofile1<<"student id\t\t"<<"student name\t\t"<<"location";
    }
    else
        ofile1<<st_id<<"\t\t"<<st_name<<"\t\t"<<st_place<<"\n";
    ofile1.close();
 
}
void file::display()
{
    ifstream nfile1;
    nfile1.open("student.txt",ios::in|ios::out);
    if(nfile1.is_open())
    {
        while(!nfile1.eof())
        {
            getline(nfile1,ch);
            cout<<ch;
        }
        nfile1.close();
    }
    else
        cout<<"failed to get values";
}
void file::search()
{
    ifstream infile;
    infile.open("student.txt",ios::in|ios::out);
    if(infile.is_open())
    {
        string sword;
        cout<<"\nEnter the search word :";
        cin>>sword;
 
        while(!infile.eof())
        {
            getline(infile,ch);
            int i,pos;
            for(i=0;i<=ch.length();i++)
                ch[i]=ch[i];
            for(i=0;i<=sword.length();i++)
                sword[i]=sword[i];
            pos=ch.find(sword);
            if(pos!=string::npos)
            {
                cout<<ch<<endl;
 
            }
            else
            {
                cout<<"word not found"<<endl;
            }
        }
        infile.close();
    }
 
}
 
int main()
{
    file obj;
    int a;
    cout<<"\n1.Insertion";
    cout<<"\n2.Display";
    cout<<"\n3.Search";
    cout<<"\nEnter your choice\t";
    cin>>a;
    switch(a)
    {
    case 1:
        obj.getdata();
        obj.putdata();
        break;
    case 2:
        obj.display();
        break;
    case 3:
        obj.search();
    }
    return 0;
}
 

[vinoth66]

i don't no how to use that bool write. i am not fresher. i have just completed my college.i don't have any work experience to know fully

[weaknessforcats]

Let's start with this function:

void file::putdata()
{
    ofstream ofile1("student.txt",ios::out|ios::binary|ios::app);
    ifstream nfile("student.text",ios::in);
    long begin,end;
    nfile.open("student.txt");
    begin = nfile.tellg();
    nfile.seekg (0, ios::end);
    end = nfile.tellg();
    nfile.close();
    if((end-begin)==0)
    {
        ofile1<<"student id\t\t"<<"student name\t\t"<<"location";
    }
    else
        ofile1<<st_id<<"\t\t"<<st_name<<"\t\t"<<st_place<<"\n";
    ofile1.close();
 
}
 

First, the function should return at least a bool. Maybe true if the function worked and false if it didn't.

Second. I would not open the file in each function. Instead I would have a data member for the ofstream and I would write an open(string) function which can be called by the other member functions. There is duplicated code in every function to open the ofstream.

Third, I would not use ios::binary. You ware writing characters and you need to be sure each record is the same size.

Fourth, after you open the file, tellg() does not position to the beginning of the file. Use seekg to ios::beg.

Fifth, all that should be in the ofstream is the data. It looks like there are column names being written, You supply the column names only when you display.

putdata should look like:

void file::putdata()
{
 ofile1<<st_id<< st_name << st_place <<\n;
}

and that's it. putdata just puts the data. It does not open the file, does not add any data of it's own, does not display data because it's not a display function.

BTW if you feel you need to display in putdata, then use an int return and return a number. Then have an error function take the int as an argument and display the error message.

Maybe you have a seekg to ios::end if this function appends to the end of the file.

Lastly, change you array size form 256 to something small, like 10. That way you can see the file on one line using notepad or vi. (I don't know what OS you are using). When everything works you can change back to 256.

Post again and I'll parse another of the functions.

[vinoth66]

sir,there is no problem in "putdata" function.

I used tellg function to use the titles only once during the compilation. To avoid the content title to print and save each and every time it is executed.

I have problem with search and getdata function.

In getdata function it does't get the data for ID(first charater) from the user Instead of that it skip to next name and place to get the data from the user.That is the problem over there.

And in search function it retrieve the data from the file that is searched but it also prints the else loop content "word not found". It checks each and every word used in the file.

To avoid overwriting and save the file i use ios::binary and ios::app(append).The task is to get id,name and place as much as user entered.

If i use string to get that when the user type the first name and space to write the second name it take the second name as a input for 3rd string and exit the loop.That is why i used char and provided it with 256 length.


May be my English for explanation of program is poor.so for understanding what i am trying to say please compile the program i also made some modification over here. say it and say.

#include <iostream>
#include<fstream>
using namespace std;
class file
{
public:
    char st_id[256],st_name[256],st_place[256];
    string ch,sword;
    void getdata();
    void putdata();
    void display();
    void search();
};
void file::getdata()
{
    ofstream ofile("student.txt",ios::out|ios::app|ios::binary);
    if(ofile.is_open())
    {
        cout<<endl;
        cout<<"\nEnter the Student Id:"<<endl;
        cin.getline(st_id,256);
        cout<<"\nEnter the name of the student:";
        cin.getline(st_name,256);
        cout<<"\nEnter the location of student:";
        cin.getline(st_place,256);
    }
    else
        cout<<"\nFailed to create and Insert";
}
void file::putdata()
{
    ofstream ofile1("student.txt",ios::out|ios::binary|ios::app);
    ifstream nfile("student.text",ios::in);
    long begin,end;
    nfile.open("student.txt");
    begin = nfile.tellg();
    nfile.seekg (0, ios::end);
    end = nfile.tellg();
    nfile.close();
    if((end-begin)==0)
    {
        ofile1<<"student id\t\t"<<"student name\t\t"<<"location";
    }
    else
        ofile1<<st_id<<"\t\t"<<st_name<<"\t\t"<<st_place<<"\n";
    ofile1.close();
 
}
void file::display()
{
    ifstream nfile1;
    nfile1.open("student.txt",ios::in|ios::out);
    if(nfile1.is_open())
    {
            while(getline(nfile1,ch))
            {
 
                int i,f=ch.find(sword);
                if(f!=string::npos)
                {
                    cout<<"line"<<"\t"<<ch<<endl;
 
                }
                else
                {
                    for(i=0;i<=sword.length();i++)
                        sword[i]=sword[i];
                    for(i=0;i<=ch.length();i++)
                        ch[i]=ch[i];
                    if(sword[i]==ch[i])
                    {
                    cout<<"word not found"<<endl;
                    }
                }
            }
            nfile1.close();
    }
    else
        cout<<"failed to get values";
}
void file::search()
{
    ifstream infile;
    infile.open("student.txt",ios::in|ios::out);
    if(infile.is_open())
    {
        string sword;
        cout<<"\nEnter the search word :";
        cin>>sword;
 
        while(!infile.eof())
        {
            getline(infile,ch);
            int i,pos;
            for(i=0;i<=ch.length();i++)
                ch[i]=ch[i];
            for(i=0;i<=sword.length();i++)
                sword[i]=sword[i];
            pos=ch.find(sword);
            if(pos!=string::npos)
            {
                cout<<ch<<endl;
 
            }
            else
            {
                cout<<"word not found"<<endl;
            }
        }
        infile.close();
    }
 
}
 
int main()
{
    file obj;
    int a;
    cout<<"\n1.Insertion";
    cout<<"\n2.Display";
    cout<<"\n3.Search";
    cout<<"\nEnter your choice\t";
    cin>>a;
    switch(a)
    {
    case 1:
        obj.getdata();
        obj.putdata();
        break;
    case 2:
        obj.display();
        break;
    case 3:
        obj.search();
    }
    return 0;
}
 

thank you

[vinoth66]

sorry my mistake(say it and say) try it and say