循环需要有进入条件和退出条件 ## for ~~~ for 变量 in 列表；do 循环体 done ~~~ ~~~ for (( expr1 ; expr2 ; expr3 )); do 循环体 done ~~~ ### 生成整数列表 ~~~ {1..100} `seq [起始数] [步进长度] 结束数` ~~~ ## while **条件满足则执行循环** ~~~ while CONDITION; do 循环体 done ~~~ while的特殊用法一，**死循环** ~~~ while :;do 循环体 done ~~~ while的特殊用法二，**按行读取文件** ~~~ while read LINE; do 循环体 done < /PATH/TO/SOMEFILE ~~~ ## until **满足条件则结束循环** ~~~ until CONDITION; do 循环体 done ~~~ ## continue 提前结束本轮循环，进入下一轮循环