1.常用操作

substring可以是正則表示式

2.一個例子

 #!/bin/bash
 mystr="hello world"
 echo ${#mystr} #11
 echo ${mystr:1} #ello world
 echo ${mystr:1:2} #el
 echo ${mystr#*l} #lo world
 echo ${mystr##*l} #d
 echo ${mystr%l*} #hello wor
 

 echo ${mystr%%l*} #he
 echo ${mystr/l/L} #heLlo world
 echo ${mystr//l/L} #heLLo worLd
 echo ${mystr/#hello/lala} #lala world
 echo ${mystr/#llo/lala} #hello world
 echo ${mystr/%world/lala} #hello lala
 echo ${mystr/%worl/lala} #hello world

需要注意的是${string/#substring/replacement}和${string/%substring/replacement}是字首匹配和字尾匹配,也就是說其它位置的匹配是無效的。