while循環?

1)?

while CONDITION; do

statement

statement

<改變循環條件真假的語句>

done?

編寫腳本，計算1---100的和?

#!/bin/bash

#

sum=0

i=1

while [ $i -le 100 ]; do

? ?let sum=$sum+$i

? ?let i=$i+1

done

echo $sum

2)?

while true; do?

statement

statement

done?

#!/bin/bash

#

while true; do

? ?read -p "請輸入你的選擇：" choice

? ?if [ $choice == "q" ]; then

? ? ?break

? ?fi

done

#!/bin/bash

#

while true; do

? ?uptime

? ?sleep 3

done

3)

while read line; do?

statement

statement

done < file?

#!/bin/bash

#

bash_num=0

nologin_num=0

while read line; do

? ?sh_name=$(echo $line | awk -F: '{print $7}')

? ?case $sh_name in

? ? ? ? /bin/bash)

? ? ? ? ? ?let bash_num=$bash_num+1

? ? ? ? ? ?;;

? ? ? ? /sbin/nologin)

? ? ? ? ? ?let nologin_num=$nologin_num+1

? ? ? ? ? ?;;

? ?esac

done < /etc/passwd

echo $bash_num

echo $nologin_num

util循環：

util CONDITION; do?

? ? statement

statement

done?

條件為假時，執行循環，條件為真時，結束循環