引言

今天一个要写一个 Shell 脚本，其中要判断 2 个字符串是否相等，
当时在这里犹豫了下，应该是使用 =或!=（用于字符串比较），和 eq/ne（用于算术比较）搞混了，这里有必要记录下。
学习就是不断地重复，不断地加深理解。

Shell 脚本中的比较条件测试操作符

Arithmetic Comparison	 	
-eq	Equal to	 			
-ne	Not equal to	 		
-lt	Less than	 			
-le	Less than or equal to	
-gt	Greater than	 		
-ge	Greater than or equal to

String Comparison	 
=	Equal to
==	Equal to
!=	Not equal to
\<	Less than (ASCII) *
\>	Greater than (ASCII) *
* If within a double-bracket [[ ... ]] test construct, then no escape \ is needed.
 
-z	String is empty
-n	String is not empty

Arithmetic Comparison	within double parentheses (( ... ))	 	 	 
>	Greater than	 	 	 
>=	Greater than or equal to	 	 	 
<	Less than	 	 	 
<=	Less than or equal to	 	 	 

Ref

ABS Table B-2. TEST Operators: Binary Comparison
Shell 字符串比较