CODEWITHSUNDEEP
c++ofstream
Lucas
Lucas

Reputation: 588

Previous lines are cleared on ofstream

I would like to write a new line with a string on a file when the writeToFile function is called. Is that possible without clearing the previous line or the whole txt?

void writeToFile(string str) {
    ofstream fileToWrite;
    fileToWrite.open("C:/Users/Lucas/Documents/apps/resultado.txt");
    if(fileToWrite.good()) {
        //write the new line without clearing the txt
                //fileToWrite << str won't work for this reason
    }
    fileToWrite.close();
}

Upvotes: 0

Views: 128

Answers (1)

Jerry Coffin
Jerry Coffin

Reputation: 490788

Yes. Look up std::ios_base::ate and std::ios_base::app.

void write_to_file(std::string const &str) { 
    std::ofstream fileToWrite("C:/Users/Lucas/Documents/apps/resultado.txt", 
                              std::ios_base::app);
    fileToWrite << str << "\n";
}

In this case, the difference between the two is irrelevant, but ios_base::ate means when you open the file, it's positioned at the end, so what you write is added to the end -- but if you want, you can seek to earlier parts of the file and overwrite what's there. With ios_base::app, before you do any write, it'll automatically seek to the end, so any writing you do gets appended to the end, rather than overwriting any existing data.

Upvotes: 2

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