Shell经典十三问

1 简介..................................................................................................................................................3
2 为何叫做 shell ？...........................................................................................................................3
3 shell prompt(PS1) 与 Carriage Return(CR) 的关系？..................................................................5
4 别人 echo、你也 echo ，是问 echo 知多少？...........................................................................7
5 “”(双引号) 与 ' '(单引号)差在哪？.............................................................................................12
6 var=value？export 前后差在哪？................................................................................................20
7 exec 跟 source 差在哪？..............................................................................................................30
8 ( ) 与 { } 差在哪？.......................................................................................................................35
9 $(( )) 与 $( ) 还有${ } 差在哪？..................................................................................................39
10 $@ 与 $* 差在哪？....................................................................................................................46
11 && 与 || 差在哪？......................................................................................................................51
12 > 与 < 差在哪？.........................................................................................................................59
13 你要 if 还是 case 呢？..............................................................................................................73
14 for what? while 与 until 差在哪？............................................................................................79
15 [^ ] 跟 [! ] 差在哪？...................................................................................................................85