bash - 文件权限中的句点是什么意思？

Question

我在“ls -l”的输出中发现了一个我不理解的权限字符:

[root@gnurr ~]# ls -l  /etc/cron.daily/
total 32
-rwxr-xr-x  1 root root  265 Sep 10 16:04 0logwatch
-rwxr-xr-x. 1 root root  118 Aug 17 12:21 cups

文件“cups”的标准权限字符后有句点，但文件“0logwatch”则没有

我到处都发现了很多这样的点——它们也出现在目录或软链接(soft link)中，但它们似乎永远不会出现在我自己创建的文件中。

我发现一些帖子在这个位置提到了“@”或“+”，意思是“扩展属性”或“扩展安全信息”，但没有提到“.”。

有人知道点是什么意思吗？

Answer 1

来自信息/手册页:

GNU 'ls' uses a '.' character to indicate a file with an SELinux security context, but no other alternate access method.

整个部分还提到了一个'+'，这是相关的:

Following the file mode bits is a single character that specifies whether an alternate access method such as an access control list applies to the file. When the character following the file mode bits is a space, there is no alternate access method. When it is a printing character, then there is such a method.

GNU 'ls' uses a '.' character to indicate a file with an SELinux security context, but no other alternate access method.

A file with any other combination of alternate access methods is marked with a '+' character.