Content-Type: text/x-zim-wiki
Wiki-Format: zim 0.4
Creation-Date: 2011-11-28T10:07:29+08:00

====== expr ======
Created Monday 28 November 2011

对表达式求值：

[geekard@geekard ~]$ expr 2 \+ 3   #算术运算符只对整数有效
5
[geekard@geekard ~]$ expr 2 \* 3.2
expr: non-integer argument
[geekard@geekard ~]$ expr 2 \* 3
6
[geekard@geekard ~]$ expr 2 \- 3
-1
[geekard@geekard ~]$ expr 2 \/ 3
0
[geekard@geekard ~]$ expr 2 \% 3
2
[geekard@geekard ~]$ expr 2 \& 3
2
[geekard@geekard ~]$ expr 2 \<= 3   #关系运算符对数字字符和字符串都是有效的
1
[geekard@geekard ~]$ expr 2 \<= 1
0
[geekard@geekard ~]$ expr 2 \= 2   
1
[geekard@geekard ~]$ expr 2 \= 3
0
[geekard@geekard ~]$ expr aff \= fdf 
0
[geekard@geekard ~]$ expr aff \= aff
1
[geekard@geekard ~]$ expr aff \>= aee
1