CODEWITHSUNDEEP
linuxwindowsmacosc++11
patrykbajos
patrykbajos

Reputation: 393

Prevent opening file in "rw" and "r" at the same time

I'm writing class to r/w files from OS file system or from my own archives format in my game engine. How can I make impossible to open file by std::fopen() or std::fstream in modes "rw" and "r". I have written some code to test that on Linux. Here's it:

#include <fstream>
#include <iostream>
using namespace std;


int main()
{
    fstream in("file.txt", ios::in | ios::out);

    if(!in.is_open())
    {
        cout << "Plik nie może być otwarty w trybie rw" << endl;
        return 1;
    }

    cout << "Plik otwarty w trybie rw" << endl;
    in << ".test.";
    cout << "Wpisano tekst" << endl;

    while(1){}

    return 0;
}

/* Drugi plik */
/* The second src code */


#include <fstream>
#include <iostream>
using namespace std;


int main()
{
    fstream in("file.txt", ios::in);

    if(!in.is_open())
    {
        cout << "Plik nie może być otwarty w trybie r" << endl;
        return 1;
    }

    cout << "Plik otwarty w trybie r" << endl;
    cout << in << endl;

    return 0;
}

When I've executed the ./rw program and some instances of ./r, the ./rw has gone into endless loop and the instances of ./r have terminated with 0 code.

Sorry for my English. :)

Upvotes: 0

Views: 98

Answers (1)

John Zwinck
John Zwinck

Reputation: 249153

You should "lock" the file using lockf(): http://man7.org/linux/man-pages/man3/lockf.3.html

Upvotes: 1

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