CODEWITHSUNDEEP
c++
Venraey
Venraey

Reputation: 297

Deleting specific line from file

These are the contents of my example file:

abcdefg hijk lmnopqrstAB CSTAKLJSKDJD KSA FIND ME akjsdkjhwjkjhasfkajbsdh ADHKJAHSKDJH

I need to find and delete the 'FIND ME' inside of the file so the output would look like this:

abcdefg hijk lmnopqrstAB CSTAKLJSKDJD KSA akjsdkjhwjkjhasfkajbsdh ADHKJAHSKDJH

I have tried the following method of doing getline and then writing all of the contents except the FIND ME into a temporary file and then rename the temporary file back.

string deleteline;
string line;

ifstream fin;
fin.open("example.txt");
ofstream temp;
temp.open("temp.txt");
cout << "Which line do you want to remove? ";
cin >> deleteline;



while (getline(fin,line))
{
    if (line != deleteline)
    {
    temp << line << endl;
    }
}

temp.close();
fin.close();
remove("example.txt");
rename("temp.txt","example.txt");

but it doesn't work. Just as a side note: the file has NO newline/linefeeds. So the file contents are all written in 1 line.

EDIT:

FIXED CODE:

while (getline(fin,line))
{
    line.replace(line.find(deleteline),deleteline.length(),"");
    temp << line << endl;

}

This gets me the results I expected. Thank you everyone for helping!

Upvotes: 16

Views: 86532

Answers (3)

Cuinn Herrick
Cuinn Herrick

Reputation: 317

In case anyone would like it I have converted Venraey's useful code into a function:

#include <iostream>
#include <fstream>
    
void eraseFileLine(std::string path, std::string eraseLine) {
    std::string line;
    std::ifstream fin;
    
    fin.open(path);
    // contents of path must be copied to a temp file then
    // renamed back to the path file
    std::ofstream temp;
    temp.open("temp.txt");

    while (getline(fin, line)) {
        // write all lines to temp other than the line marked for erasing
        if (line != eraseLine)
            temp << line << std::endl;
    }

    temp.close();
    fin.close();

    // required conversion for remove and rename functions
    const char * p = path.c_str();
    remove(p);
    rename("temp.txt", p);
}

Upvotes: 9

X1NK3R
X1NK3R

Reputation: 11

I'd like to clarify something. Although the answer provided by gmas80 could work, for me, it didn't. I had to modify it somewhat, and here's what I ended up with:

position = line.find(deleteLine);

if (position != string::npos) {
    line.replace(line.find(deleteLine), deleteLine.length(), "");
}

Another thing that didn't satisfy me was that it left blank lines in the code. So I wrote another thing to delete the blank lines:

if (!line.empty()) {
    temp << line << endl;
}

Upvotes: 0

gmas80
gmas80

Reputation: 1268

Try this:

line.replace(line.find(deleteline),deleteline.length(),"");

Upvotes: 4

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