Delete the content of file?!

[sivar]

Hi every one!
I need to delete the content specific text in txt file within C++
I have use the code following but it delete all content of it!

case 5:
		{
				string line, name;
				cout << "Please Enter the name of record you want to delete: ";
				cin >> name;
				ifstream myfile;
				ofstream outfile;
				myfile.open("StudentInformation.txt");
				outfile.open("StudentInformation.txt");
				
				while (!myfile.eof()) {
					myfile>>line;	
					if(line==search){
						if(line==";")
						cout<< myfile.eof() << endl;
						break;
					}
				}
				
				cout << "The record with the name " << name << " has been deleted if it exsisted" << endl;
				myfile.close();
				outfile.close();
			
		}

for example if i have those content in the file:

Name:Sivar
ID:1
Kurdish:4
Arabic:76
English:87
Mathematic:67
Physics:65
Biology:54
Chemical:87
Average = 62
;

Name:Jack
ID:2
Kurdish:67
Arabic:89
English:67
Mathematic:65
Physics:76
Biology:87
Chemical:89
Average = 77
;

Name:Sandy
ID:3
Kurdish:34
Arabic:65
English:76
Mathematic:89
Physics:65
Biology:54
Chemical:98
Average = 68
;





Then if I type "Jack"'s name , it delete jack's information and the content of file becomes as bellow!

Name:Sivar
ID:1
Kurdish:4
Arabic:76
English:87
Mathematic:67
Physics:65
Biology:54
Chemical:87
Average = 62
;

Name:Sandy
ID:3
Kurdish:34
Arabic:65
English:76
Mathematic:89
Physics:65
Biology:54
Chemical:98
Average = 68
;

[codekiddy]

Hi,
If you wan to delete a line containing a string "search" you can use getline:

#include <string>
#include <fstream>

int main()
{
	using namespace std;
	string input;
	string search = "John";
	fstream file;

	file.open("file_name.txt", ios::in);

	if (file.is_open())
	{
		while (!file.eof())
		{
			getline(file, input);
			if (input.find(search) != string::npos); // check if "John" is found
			{
				// perform delete operation here
				break;
			}
		}
                file.close();
	}
	return 0;
}

[benbalach]

It's because you are opening the file twice with 2 different file streams. Just use 1 std::fstream.

[sivar]

@codekiddy
@benbalach
I know how to search for a specific name information and output it, but my problem is that how to delete them, i don't know which code are using to do this,, or i haven't any idea how to delete them?!!!!

[codekiddy]

Hi sivar,

following example will show you how to delete an entry from the file, however you'll need to redesign it for your needs.

#include <string>
#include <fstream>
#include <iostream>

int main()
{
	using namespace std;
	string input;
	string changed_content;
	string search = "John";
	fstream file;
	string file_name = "C:\\path\\to\\file\\file.txt";

	file.open(file_name, ios::in);

	if (file.is_open())
	{
		while (!file.eof())
		{
			getline(file, input);

			if (input.find(search) == string::npos) // check if "John" is not here
			{
				changed_content += input;
				changed_content += '\n';
			}

			input.clear(); // delete input for new loop
		}
		file.close();
		file.open(file_name, ios::out | ios::trunc); // reopen file and clear it's contents
		if (file.is_open())
		{
			file << changed_content; // wite stuff back into the file without john
			file.close();
		}
		else
		{
			cout << "file for rewrite not open\n";
		}
	}
	else
	{
		cout << "file for input not open\n";
	}
	return 0;
}