#! /bin/bash i=0 while [ $i -lt 5 ] #While i is less than 5 do echo "i is currently $i" i=$[$i+1] #Not the lack of spaces around the brackets. This makes it a not a test expression done #ends the loop
在测试期间（在while语句之后），请注意括号内有空格。这些空间是必需的。
该循环输出：
i is currently 0 i is currently 1 i is currently 2 i is currently 3 i is currently 4