shell while 循环
认识while循环用法一、死循环，：在while循环里面表示永久为真
# cat 7.sh
#!/bin/bash
while :
do
date +%T
sleep 5
done
用法二、顺序输出1-10
# cat 8.sh
#!/bin/bash
n=1
while [ $n -le 10 ]
do
echo $n
n=$[$n+1]
done
用法三、检测用户输入
# cat 9.sh
#!/bin/bash
while :
do
read -p "Please input a number: " m
n=`echo $m | sed 's///g'`
if [ -z "$n" ]
then
echo $m
exit
fi
done
用法四、检测用户输入
# cat 9.sh
#!/bin/bash
n=1
while [ ! -z "$n" ]
do
read -p "Please input a number: " m
n=`echo $m | sed 's///g'`
echo $m
done
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