运算符优先级递减的顺序如下：
算术和逻辑运算符：
| 运算符 | 描述 |
|---|---|
| ( ) | Change precedence |
| ~ | 1's complement |
| ! | Logical negation |
| * | Multiply |
| / | Divide |
| % | Modulo |
| + | Add |
| - | Subtract |
| << | Left shift |
| >> | Right shift |
| == | String comparison for equality |
| != | String comparison for non equality |
| =~ | Pattern matching |
| & | Bitwise "and" |
| ^ | Bitwise "exclusive or" |
| | | Bitwise "inclusive or" |
| && | Logical "and" |
| || | Logical "or" |
| ++ | Increment |
| -- | Decrement |
| = | Assignment |
| *= | Multiply left side by right side and update left side |
| /= | Divide left side by right side and update left side |
| += | Add left side to right side and update left side |
| -= | Subtract left side from right side and update left side |
| ^= | "Exclusive or" left side to right side and update left side |
| %= | Divide left by right side and update left side with remainder |
文件测试操作：
有以下操作测试与Unix文件相关联的各种属性。
| 操作符 | 描述 |
|---|---|
| -r file | Checks if file is readable if yes then condition becomes true. |
| -w file | Check if file is writable if yes then condition becomes true. |
| -x file | Check if file is execute if yes then condition becomes true. |
| -f file | Check if file is an ordinary file as opposed to a directory or special file if yes then condition becomes true. |
| -z file | Check if file has size greater than 0 if yes then condition becomes true. |
| -d file | Check if file is a directory if yes then condition becomes true. |
| -e file | Check if file exists. Is true even if file is a directory but exists. |
| -o file | Check if user owns the file. It returns true if user is the owner of the file. |
更多建议：