文件锁怎么用php_php文件锁机制使用方法与注意事项

$fp = fopen("log.txt", "a");
if (flock($fp, LOCK_EX)) {
    fwrite($fp, "记录一条日志\n");
    flock($fp, LOCK_UN); // 释放锁
} else {
    echo "无法获取锁";
}
fclose($fp);

$fp = fopen("data.txt", "r+");
if (flock($fp, LOCK_EX | LOCK_NB)) {
    // 成功获取锁，进行写操作
    ftruncate($fp, 0);
    fwrite($fp, "新数据");
    flock($fp, LOCK_UN);
} else {
    echo "文件正被占用，稍后重试";
}
fclose($fp);
</font>

<p>如需实现超时等待，可结合循环和sleep：</p>
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<font size="2">
<pre class="brush:php;toolbar:false;">
$attempts = 0;
while (!flock($fp, LOCK_EX | LOCK_NB) && $attempts < 5) {
    usleep(200000); // 等待200ms
    $attempts++;
}

$lockFile = fopen("/tmp/update.lock", "w");
if (!flock($lockFile, LOCK_EX | LOCK_NB)) {
    die("已有进程在运行");
}
// 执行任务...
flock($lockFile, LOCK_UN);
fclose($lockFile);