文件锁

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文件锁

可以锁整个文件或者一部分

TODO测试代码

stdio提供了一个简单的接口

   #include <stdio.h>

   void flockfile(FILE *filehandle);
   int ftrylockfile(FILE *filehandle);
   void funlockfile(FILE *filehandle);

通过fcntl和struct flock

通过fcntl和struct flock可以实现更复杂的功能，比如只锁住某个区间

以下是nginx的相关代码

ngx_err_t
ngx_trylock_fd(ngx_fd_t fd)
{
    struct flock  fl;

    ngx_memzero(&fl, sizeof(struct flock));
    fl.l_type = F_WRLCK;
    fl.l_whence = SEEK_SET;

    if (fcntl(fd, F_SETLK, &fl) == -1) {
        return ngx_errno;
    }

    return 0;
}


ngx_err_t
ngx_lock_fd(ngx_fd_t fd)
{
    struct flock  fl;

    ngx_memzero(&fl, sizeof(struct flock));
    fl.l_type = F_WRLCK;
    fl.l_whence = SEEK_SET;

    if (fcntl(fd, F_SETLKW, &fl) == -1) {
        return ngx_errno;
    }

    return 0;
}


ngx_err_t
ngx_unlock_fd(ngx_fd_t fd)
{
    struct flock  fl;

    ngx_memzero(&fl, sizeof(struct flock));
    fl.l_type = F_UNLCK;
    fl.l_whence = SEEK_SET;

    if (fcntl(fd, F_SETLK, &fl) == -1) {
        return  ngx_errno;
    }

    return 0;
}

https://blog.csdn.net/wallwind/article/details/7816221 https://www.cnblogs.com/kex1n/p/7100107.html

The End