shell while 循環

認識while循環

用法1、死循環，：在while循環裏面表示永久爲真

[root@localhost test]# cat 7.sh

#!/bin/bash

while :

do

date +%T

sleep 5

done

用法2、順序輸出1-10

[root@localhost test]# cat 8.sh

#!/bin/bash

n=1

while [ $n -le 10 ]

do

echo $n

n=$[$n+1]

done

用法3、檢測用戶輸入

[root@localhost test]# cat 9.sh

#!/bin/bash

while :

do

read -p "Please input a number: " m

n=`echo $m | sed 's/[0-9]//g'`

if [ -z "$n" ]

then

echo $m

exit

fi

done

用法4、檢測用戶輸入

[root@localhost test]# cat 9.sh

#!/bin/bash

n=1

while [ ! -z "$n" ]

do

read -p "Please input a number: " m

n=`echo $m | sed 's/[0-9]//g'`

echo $m

done