該結構是在lock.h檔案中定義。

lock.h File

功能

定義一些檔案的鎖的選項

Description

The flockstructure in the/usr/include/sys/flock.hfile, which describes a lock, contains the following fields:

看一下示例吧！

int
waldirlock(Wal *w)
{
    int r;
    int fd;
    struct flock lk;
    char path[PATH_MAX];

    r = snprintf(path, PATH_MAX, "%s/lock", w->dir);
    if (r > PATH_MAX) {
        twarnx("path too long: %s/lock", w->dir);
        return 0;
    }

    fd = open(path, O_WRONLY|O_CREAT, 0600);
    if (fd == -1) {
        twarn("open");
        return 0;
    }

    lk.l_type = F_WRLCK;
    lk.l_whence = SEEK_SET;
    lk.l_start = 0;
    lk.l_len = 0;
    r = fcntl(fd, F_SETLK, &lk);
    if (r) {
        twarn("fcntl");
        return 0;
    }

    // intentionally leak fd, since we never want to close it
    // and we'll never need it again
    return 1;
}

struct flock 作為fcntl函式的第三個引數，使用F_SETLK,設定了其引數。