while

while是只要符合条件就执行，执行完毕之后再判断是否符合条件，符合条件继续执行，一直循环重复，直到有退出指令。

[alvin@poppy ~]$ vim while.sh
[alvin@poppy ~]$ chmod +x while.sh
[alvin@poppy ~]$ cat while.sh
#!/bin/bash


name='alvin'

while [ $name == 'alvin' ]
do
    echo name is $name
    sleep 1
done
[alvin@poppy ~]$ ./while.sh
name is alvin
name is alvin
name is alvin
name is alvin
name is alvin
^C