Deleting Text File Record

Hello,
I am trying to write a function that searches for, and deletes, a particular record in a text file. I am trying to achieve this by creating a temporary file, copy everything except the record i want to delete, delete the original file, and then rename the temp file using the original name. However, my code does not delete the record, and instead, sometimes copies the contents of the original file and appends.

Can anyone tell me where I went wrong, or show me a better way. Thanks in advance.

Code:

void POS::deleteRecord(char fileName[], string itemNum) { ofstream write; ifstream read; counter = 0; string num, name, manu, type, reso, cost, pric, quan; read.open(fileName); write.open("temp.txt", ios::out); write << ""; // empty the file just in case; getline(read, num); getline(read, name); getline(read, manu); getline(read, type); getline(read, reso); getline(read, cost); getline(read, pric); getline(read, quan); getline(read, readSpace); while (!read.fail()) { if (itemNum.compare(num)== 0) // is item number == to our search item? { num = ""; name = ""; manu = ""; type = ""; reso = ""; cost = ""; pric = ""; quan = ""; readSpace = ""; continue; // skip and move to the next record } else { counter++; // store only valid records (quantity > 0) write << counter << endl << name << endl << manu << endl << type << endl << reso << endl << cost << endl << pric << endl << quan << endl << endl; }// end else getline(read, num); getline(read, name); getline(read, manu); getline(read, type); getline(read, reso); getline(read, cost); getline(read, pric); getline(read, quan); getline(read, readSpace); }// end while read.close(); write.close(); // delete the original file remove (fileName); int result; // rename the temp file to original name result = rename("temp.txt", "Printers.txt"); if (result == 0) cout << " Successfully!"; else cout << " Unsuccessful!"; remove("temp.txt"); // reset counters counter = 0; }

I also tried vectors but now I am getting a "Permission Denied" error message and now every time I try to rerun the program, it just freezes! Any suggestions will be greatly appreciated.

Code:

# include <iostream> # include <vector> # include <fstream> # include <algorithm> using namespace std; int main() { ifstream infile; ofstream outfile; int counter = 0; string searchItem; cout << "Enter search Item: "; cin >> searchItem; infile.open("test.txt"); outfile.open("outfile.txt"); outfile << ""; vector<string> info(9); getline(infile, info[0]); getline(infile, info[1]); getline(infile, info[2]); getline(infile, info[3]); getline(infile, info[4]); getline(infile, info[5]); getline(infile, info[6]); getline(infile, info[7]); getline(infile, info[8]);// space while (!infile.fail()) { if (info[0].compare(searchItem) == 0) info.erase(info.begin(), info.begin()+8); else { counter++; outfile << counter << endl << info[1] << endl << info[2] << endl << info[3] << endl << info[4] << endl << info[5] << endl << info[6] << endl << info[7] << endl << info[8] << endl; // output a space } getline(infile, info[0]); getline(infile, info[1]); getline(infile, info[2]); getline(infile, info[3]); getline(infile, info[4]); getline(infile, info[5]); getline(infile, info[6]); getline(infile, info[7]); getline(infile,info[8]); }// end while infile.clear(); infile.seekg(0); infile.close(); outfile.close(); system ("pause"); }

Code:

write << ""; // empty the file just in case;

That won't empty the file. All it will do is write a string to the file, and the string has zero characters in it -- so you're really just doing nothing. I think whatever remained in the file will still be there (unless ios::out creates a new file; I don't know it well enough to say). If you want to truncate the file, use ios::trunc. Input/Output with files Or you can just use ofstream -- that will create a new file for you.

Your input file does exist, right?

Thanks for your reply DWK. I found the reason why my original file kept growing: I had a function call that had some faulty code in it. Any way I got it to delete with the following code. Please feel free to suggest a more effecient or better solution. Thanks again.

Code:

void POS::deleteRecord(char fileName[], string itemNum) { // objects for writing and reading ofstream write; ifstream read; counter = 0; // used for renumbering records after deletion // variables for storing record details string num, name, manu, type, reso, cost, pric, quan; write.open("temp.txt", ios::out); // open temp file for storing valid records write << ""; // empty file just in case. read.open("Printers.txt"); // open file for reading // read first record on file getline(read, num); getline(read, name); getline(read, manu); getline(read, type); getline(read, reso); getline(read, cost); getline(read, pric); getline(read, quan); getline(read, readSpace); // store space as well // read file until no more records exist while(!read.fail()) { if (itemNum.compare(num)== 0) // if record's num equals our search item { // delete record num.erase(num.begin(), num.end()); // delete every character of record name.erase(name.begin(), name.end()); manu.erase(manu.begin(),manu.end()); type.erase(type.begin(),type.end()); reso.erase(reso.begin(),reso.end()); cost.erase(cost.begin(),cost.end()); pric.erase(pric.begin(),pric.end()); quan.erase(quan.begin(),quan.end()); }// end if else // else store only valid records (quantity > 0) { counter++; // new item counter write << counter << endl // insert new item numbering << name << endl << manu << endl << type << endl << reso << endl << cost << endl << pric << endl << quan << endl << endl; // inserts a space between records }// end else // read another record getline(read, num); getline(read, name); getline(read, manu); getline(read, type); getline(read, reso); getline(read, cost); getline(read, pric); getline(read, quan); getline(read, readSpace); // store space as well }// end while // reset counter counter = 0; // reposition to beginning and close files read.clear(); read.seekg(0); read.close(); write.close(); // open files again read.open("temp.txt"); write.open("Printers.txt",ios::out); write << ""; // clear original file // read from temp file getline(read, num); getline(read, name); getline(read, manu); getline(read, type); getline(read, reso); getline(read, cost); getline(read, pric); getline(read, quan); getline(read, readSpace); // store space as well while(!read.fail()) { // write back to the original file the amended information write << num << endl // insert new item numbering << name << endl << manu << endl << type << endl << reso << endl << cost << endl << pric << endl << quan << endl << endl; // inserts a space between records // read another record getline(read, num); getline(read, name); getline(read, manu); getline(read, type); getline(read, reso); getline(read, cost); getline(read, pric); getline(read, quan); getline(read, readSpace); // store space as well }// end while // reposition to beginning of temp file and close files read.clear(); read.seekg(0); read.close(); write.close(); // open temp and clear contents write.open("temp.txt", ios::out); write << ""; write.close(); }

This is really too much code for what it does! There must be a more efficient way?

Create a record class then overload operator>> for std::istream and overload operator<< for std::ostream for the class.