File Permission

The output uses characters like r for reading, w for writing, and x for executing files. The combination of these operations can also be represented by a single number, called octal notation. We will use the proper number later to change the permissions.
Allowed operations | Number :- | :- Nothing (—) | 0 Execute (–x) | 1 Write (-w-) | 2 Read (r–) | 4 Write and execute (-wx) | 3 Read and execute (r-x) | 5 Read and write (rw-) | 6 Read, write, and execute (rwx) | 7
When we put together the proper numbers for the user owner, group owner and other users, we will arrive at a three digit number, like 400 for r-------- or 777 for rwxrwxrwx. [Petr Stříbný, "Command Line Handbook"]

输出使用像r（读取）、w（写入）和x（执行文件）这样的字符。这些操作的组合也可以用一个称为八进制表示法的数字来表示。我们稍后会使用正确的数字来更改权限。
允许的操作 | 数字 :- | :- 无 (—) | 0 执行 (–x) | 1 写入 (-w-) | 2 读取 (r–) | 4 写入和执行 (-wx) | 3 读取和执行 (r-x) | 5 读取和写入 (rw-) | 6 读取、写入和执行 (rwx) | 7
当我们将用户拥有者、组拥有者和其他用户的正确数字组合在一起时，最终会得到一个三位数，比如400代表r--------或者777代表rwxrwxrwx。 [Petr Stříbný, "Command Line Handbook"]