linux 多线程文件锁

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

void lock_file(int fd) {
    struct flock fl;
    fl.l_type = F_WRLCK;  // 独占锁
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;  // 锁定整个文件
    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;  // 解锁
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;  // 解锁整个文件
    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);
    printf("File locked, performing write operation...\n");
    // 执行文件写操作
    fseek(fd, 0, SEEK_END);
    fprintf(fd, "Writing to the file...\n");
    fflush(fd);

    unlock_file(fd);
    printf("File unlocked.\n");

    close(fd);
    return 0;
}