"'main': identifier not found" error in c++

Question

I keep getting this error and have no idea how to fix it because I don't see anything wrong with my code.

#include <iostream>
#include <string>
#include <fstream>
#include <algorithm>

#define GREEN "\033[32m"
#define RED   "\033[31m"
#define RESET "\033[0m"

void file_create(std::string name) {
    std::ifstream file(name);
    if (file.is_open()) {
    file.close();
    std::cout << "File already exists..." << std::endl;
    main();
    } 
    else {
    file.close(); std::ofstream newFile(name);
    if (newFile.is_open())
    std::cout << GREEN "New file successfully created..." << RESET << std::endl;
    else
    std::cout << RED "File could not be created" << RESET << std::endl;
    newFile.close();
    }
}

int main() {

}

In C++ it's not allowed to call the [`main`](https://en.cppreference.com/w/cpp/language/main_function) function yourself. If you want a loop, use an actual loop in the `main` function instead. — Some programmer dude, Oct 25 '21 at 17:27
With that said, the error is because in C++ you must *declare* all symbols before you try to use them. This should have been quite clear in any decent book, class or tutorial. — Some programmer dude, Oct 25 '21 at 17:27

score 0 · Answer 1 · answered Oct 25 '21 at 17:58

The main function is not intended to be invoked from your code. It is also a nonsense since it is called automatically when program starts. But if you need some alternative main to be invoked upon some condition, you can call it inside your main function

...
int alternative_main()
{
   place your program there
}
...
void file_create(std::string name) {
    ...
    if (file.is_open()) {
    ...
    alternative_main()
    } 
    else {
    ...
    }
}

Suppose your main looks like this

int main() {
   file_create("myfile");
}

score 0 · Answer 2 · answered Nov 01 '21 at 18:23

#include <iostream>
#include <string>
#include <fstream>
#include <algorithm>

#define GREEN "\033[32m"
#define RED   "\033[31m"
#define RESET "\033[0m"

int main(); // defined before file_create

void file_create(std::string name) {
    std::ifstream file(name);
    if (file.is_open()) {
    file.close();
    std::cout << "File already exists..." << std::endl;
    main();
    } 
    else {
    file.close(); std::ofstream newFile(name);
    if (newFile.is_open())
    std::cout << GREEN "New file successfully created..." << RESET << std::endl;
    else
    std::cout << RED "File could not be created" << RESET << std::endl;
    newFile.close();
    }
}

int main() {

}

Define int main() above file_create() so you can call it in file_create

score -2 · Answer 3 · answered Oct 25 '21 at 17:56

#include <iostream>
#include <string>
#include <fstream>
#include <algorithm>
using namespace std;
//use this instead of repetitively using std all the time
   

#define GREEN "\033[32m"
#define RED   "\033[31m"
#define RESET "\033[0m"

void file_create(string name) {
    ifstream file(name);
    if (file.is_open()) {
    file.close();
    cout << "File already exists..." << endl;
    return 0;
    } 
    else {
    file.close(); 
    ofstream newFile(name);
    if (newFile.is_open())
    cout << GREEN "New file successfully created..." << RESET << endl;
    else
    cout << RED "File could not be created" << RESET << endl;
    newFile.close();
    }
}


int main() {
string name;
cin>>name;
file_create(name);


}


try using this way...

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). — Community, Oct 25 '21 at 18:17
[Don’t](https://stackoverflow.com/questions/1452721) write `using namespace std;`. — JDługosz, Oct 25 '21 at 18:23

"'main': identifier not found" error in c++

3 Answers3