shell 十三问

学习linux编程的极品。

shell 十三问

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1) 为何叫做 shell ？ .................................................................................................................................................2

2) shell prompt(PS1) 与 Carriage Return(CR) 的关系？................................................................................................3

3) 别人 echo、你也 echo ，是问 echo 知多少？ ......................................................................................................4

4) " "(双引号) 与 ' '(单引号)差在哪？ .........................................................................................................................7

5) var=value？export 前后差在哪？ .......................................................................................................................... 11

6) exec 跟 source 差在哪？ ..................................................................................................................................... 15

7) ( ) 与 { } 差在哪？ ............................................................................................................................................. 17

8) $(( )) 与 $( ) 还有${ } 差在哪？.......................................................................................................................... 19

9) $@ 与 $* 差在哪？ ............................................................................................................................................ 22

10) && 与 || 差在哪？ ............................................................................................................................................ 24

11) > 与 < 差在哪？ ............................................................................................................................................... 27

12) 你要 if 还是 case 呢？..................................................................................................................................... 34

13) for what? while 与 until 差在哪？...................................................................................................................... 37