linux lock ex

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

void lock_file(int fd, int type) {
    struct flock fl;
    fl.l_type = type;    // F_RDLCK for shared, F_WRLCK for exclusive
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;        // Lock the entire file

    if (fcntl(fd, F_SETLKW, &fl) == -1) {
        perror("fcntl");
        exit(EXIT_FAILURE);
    }
}

void unlock_file(int fd) {
    struct flock fl;
    fl.l_type = F_UNLCK;
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;

    if (fcntl(fd, F_SETLK, &fl) == -1) {
        perror("fcntl");
        exit(EXIT_FAILURE);
    }
}

int main() {
    int fd = open("example.txt", O_RDWR);
    if (fd == -1) {
        perror("open");
        exit(EXIT_FAILURE);
    }

    lock_file(fd, F_WRLCK);  // Acquire an exclusive lock
    // Perform file operations here
    unlock_file(fd);        // Release the lock

    close(fd);
    return 0;
}