#include <iostream>

#include <unistd.h>
#include <fcntl.h>

using namespace std;

int main(int argc, char **argv) {
    if (argc <= 1) {
        cout << "Please provide path to a file" << endl;
        return 1;
    }   

    const auto filepath = argv[1];
    cout << "Testing with " << filepath << endl;

    int fd = open(filepath, O_RDWR);
    cout << "Got new file descriptor " << fd << endl;


    struct flock lock;
    lock.l_type = F_WRLCK;
    lock.l_whence = SEEK_SET;
    lock.l_start = 0;
    lock.l_len = 0;
    int code = fcntl(fd, F_SETLK, &lock);
    cout << "Lock set: " << (code == 0) << endl;

    int fd2 = open(filepath, O_RDONLY);
    cout << "Second file descriptor " << fd2 << endl;

    char c = 'x';
    int count = read(fd2, &c, 1);
    cout << "Read from second fd: " << c << " count: " << count << endl;

    int fd3 = open(filepath, O_WRONLY|O_APPEND);
    cout << "Third file descriptor " << fd3 << endl;

    c = 'o';
    count = write(fd3, &c, 1);
    cout << "Wrote to third fd: " << count << endl;
}