add another file to the end of the current file by using functions in c++

Question

I want to copy the content of another file to the end of the current file I am using. The code runs, but nothing happens in the file. This is part of the code:

void copyFile(fstream &TEXT, char *Name){
    TEXT.close();
    TEXT.open(Name, ios::in);
    char* character = (char *) malloc(sizeof(char) * 100);
    cin.clear();
    //cin.getline(character, 1000, '\0');
    cout << "Enter File Name: ";
    cin.ignore();
    cin.getline(Name, 100, '\n');;
    TEXT.open(Name, ios::out | ios::app);
    TEXT << " " << character;
    cout << "Done copying..\n";
}

Also, `TEXT.open(..., ios::in);` followed by `TEXT.open(..., ios::out | ios::app);`? — Some programmer dude, Apr 04 '18 at 19:37
Why is this tagged as C++? It looks like C (except for the `cin` usage). Also; could you post a [mcve] rather than a code snippet? — Jesper Juhl, Apr 04 '18 at 19:59
Would recommend getting a [good book](https://stackoverflow.com/q/388242/9254539) instead of whatever you're learning "C++" from currently. — eesiraed, Apr 05 '18 at 00:42

score 1 · Answer 1 · answered Apr 04 '18 at 20:15

I see a number of problems with this code:

allocating character using malloc() instead of new[], and then not reading anything into character before writing it to file, and not deallocating character.
opening TEXT with ios::in, not reading anything from it, and then reopening it with ios::out | ios::app without close()'ing it first.
reading user input into the memory that Name points to, which may or may not be large enough to hold the user input, or may be pointing at read-only memory, etc.

It is really difficult to figure out what your code is trying to do. But I think you might try something more like this instead:

void copyFile(fstream &TEXT, char *Name) {
    TEXT.close();
    TEXT.open(Name, ios::in);
    ostringstream ss;
    ss << TEXT.rdbuf();
    TEXT.close();
    cout << "Enter File Name: ";
    string otherName;
    getline(cin, otherName);
    TEXT.open(otherName.c_str(), ios::out | ios::app);
    TEXT << " " << ss.str();
    cout << "Done copying..\n";
}

Or, maybe you want something more like this:

void copyFile(fstream &TEXT, char *Name){
    ifstream ifs(Name);
    cout << "Enter File Name: ";
    string otherName;
    getline(cin, otherName);
    TEXT.close();
    TEXT.open(otherName.c_str(), ios::out | ios::app);
    TEXT << " " << ifs.rdbuf();
    cout << "Done copying..\n";
}

Or, maybe simply this:

void copyFile(fstream &TEXT, char *Name) {
    ifstream ifs(Name);
    TEXT << " " << ifs.rdbuf();
    cout << "Done copying..\n";
}

add another file to the end of the current file by using functions in c++

1 Answers1