shell脚本控制流命令的操作

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18 until loops while f o r if then else 181 e c h o 4 s h e l l s h e l l exit n n s h e l l e x i t e x i t e x i t s h e l l 0 1 s h e l l s h e l l s h e l l 1 9 s h e l l s h e l l 182 18 161 s h e l l 1821 i f t h e n e l s e c a s e 1822 0 1 for Until While w h i l e u n t i l 3 f o r f o r e c h o L I N U X B S D e c h o echo e n U N I X V B S D e c h o 1 9 e c h o s h e l l 183 if then else i f 0 1 i f if 1 then elif then else 2 3 1 2 s h e l l ......