Shell编程进阶 1.9 while循环

while 死循环

vim while.sh

#！/bin/bash
##
while ：
do
    date +%T
    sleep 3
done

： 永久帧

查看时间

3秒循环1次

 

打印1-10

#!/bin/bash
##
n=1
while [ $n -le 10 ]
do
    echo $n
    n=$[$n+1]
done

 

交互循环

#!/bin/bash
##
n=0
while [ ! -z "$n"  ]
do
    read -p "Please input a number:" m
    n=`echo $m |sed 's/[0-9]//g'`
    echo $m
done

先给n赋值

$n为空循环结束

输入数值赋值$m

$n=$m的数字被空格替换，

输出$m

 

#!/bin/bash
##
while :
do
        read -p "Please input anumber:" m
        n=`echo $m |sed 's/[0-9]//g'`
        if [ -z "$n" ]
        then
                echo $m
        exit
        else
                echo "Not is a number."
        fi
done