PHP filemtime 函数-“统计失败”
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PHP filemtime function - "stat failed for"
提问by lbednaszynski
I have a problem with PHP filemtime function. In my webapp I use Smarty template engine with caching option. In my webapp I can do some actions which generate error, but lets focus on only one action. When I click link on page some content is updated - I can click few times and everything is OK but about one request on 10 fails. Following error occurs:
我的 PHP filemtime 函数有问题。在我的 webapp 中，我使用带有缓存选项的 Smarty 模板引擎。在我的 web 应用程序中，我可以执行一些会产生错误的操作，但让我们只关注一个操作。当我点击页面上的链接时，一些内容会更新 - 我可以点击几次，一切正常，但大约 10 个请求失败。出现以下错误：
filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for
and the line that causes the problem:
以及导致问题的行：
return ($_template->getCachedFilepath() && file_exists($_template->getCachedFilepath())) ? filemtime($_template->getCachedFilepath()) : false ;
As you can see, file exists because it is checked.
如您所见，文件存在是因为它被选中。
Problematic line of code is included in smarty_internal_cacheresource_file.php(part of Smarty lib v3.0.6)
有问题的代码行包含在smarty_internal_cacheresource_file.php（Smarty lib v3.0.6 的一部分）中
App is run on UNIX system, external hosting.
应用在 UNIX 系统上运行，外部托管。
Any ideas? Should I post more details?
有任何想法吗？我应该发布更多细节吗？
回答by phihag
file_existsinternally uses the accesssystem call which checks permissions as the realuser, whereas filemtimeuses stat, which performs the check as the effectiveuser. Therefore, the problem may be rooted in the assumption of effective user == real user, which does not hold. Another explanation would be that the file gets deleted between the two calls.
file_exists内部使用access系统调用作为真实用户检查权限，而filemtime使用stat，它作为有效用户执行检查。因此，问题可能源于有效用户==真实用户的假设，该假设不成立。另一种解释是文件在两次调用之间被删除。
Since both the result of $_template->getCachedFilepath()and the existance of the file can change in between system calls, why do you call file_existsat all? Instead, I'd suggest just
既然$_template->getCachedFilepath()文件的结果和存在都可以在系统调用之间改变，你为什么要调用file_exists呢？相反，我建议只是
return @filemtime($_template->getCachedFilepath());
If $_template->getCachedFilepath()can be set to a dummy value such as false, use the following:
如果$_template->getCachedFilepath()可以设置为虚拟值，例如false，请使用以下内容：
$path = $_template->getCachedFilepath();
if (!$path) return false;
return @filemtime($path);
回答by Jeff
I used filemtime successfully without checking "file_exists" for years. The way I have always interpreted the documentation is that FALSE should be returned from "filemtime" upon any error. Then a few days ago something very weird occurred. If the file did not exist, my Cron job terminated with a result. The result was not in the program output but rather in the Cron output. The message was "file length exceeded". I knew the Cron job ended on the filemtime statement because I sent myself an email before and after that statement. The "after" email never arrived.
多年来，我成功地使用了 filemtime，而没有检查“file_exists”。我一直解释文档的方式是在出现任何错误时都应该从“filemtime”返回 FALSE。然后前几天发生了一件非常奇怪的事情。如果该文件不存在，我的 Cron 作业就会终止。结果不在程序输出中，而是在 Cron 输出中。消息是“超出文件长度”。我知道 Cron 作业以 filemtime 语句结束，因为我在该语句之前和之后给自己发送了一封电子邮件。“之后”电子邮件从未到达。
I inserted a file_exists check on the file to fix the Cron job. However, that should not have been necessary. I still do not know what was changed on the hosting server I use. Several other Cron jobs started failing on the same day. I do not know yet whether they have anything to do with filemtime.
我在文件上插入了 file_exists 检查以修复 Cron 作业。然而，这本不应该是必要的。我仍然不知道我使用的托管服务器上发生了什么变化。其他几个 Cron 作业在同一天开始失败。我还不知道它们是否与文件时间有关。
