Edit and delete data in file C/C++

Question

1.00/5 (1 vote)

See more:

Hellow!
I want to edit and delete data in file(C/C++).

What I have tried:

I have tried this method

C++

 ifstream read, read1;
ofstream write, write1;

read.open("File.txt", ios::in);
write.open("Temp.txt");

int old, New, a;
cout << "Enter number you want to edit = ";
cin >> old;

cout << "Enter new number to replace ";
cin >> New;

while (!read.eof()) {
    read >> a;

    if (a == old) { write << New << endl; }
    else          { write << a << endl;   }
}

read.close();
write.close();

read1.open("Temp.txt", ios::app);
write1.open("File.txt");

while (!read1.eof()) {
    read1 >> a;
    write1 << a << endl;
}

And this code work well.
But the issue is that this process is very slow. I mean if there are thousand of lines in file and i want to edit or delete just one line then the process is very slow.
So i need some algorithm by using that i can able to edit or delete just that line i want.
So is there any algorithm or Function?

Thanks!

Posted 29-May-18 23:23pm

Usama Iftikhar Butt

Updated 30-May-18 0:33am

Add a Solution

2 solutions

Solution 2

I would do the following:

1) read the full file in a string
2) make than a string replace
3) and write the file

use std::string for supporting my plan ;-)

Posted 30-May-18 0:34am

KarstenK

Comments

Usama Iftikhar Butt 30-May-18 11:32am

can you explain your idea little bit more

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Jochen Arndt · Accepted Answer · 2018-05-30T00:19:00

You can avoid the second while loop which is just copying the content. Instead delete File.txt and then rename Temp.txt:

C++

// Deleting the file is only necessary if the used C library 
//  implementation does not support renaming to an existing file
remove("File.txt");
rename("Temp.txt", "File.txt");

That will make your application run about half the time of your code with large files.