read命令用于从终端或文件中读取用户输入，它读取整行输入，如果没有指定名称，读取的行被赋值给内部变量REPLY。
read命令常用选项：-a，-p，-s，-t，-n

$read
hello
$echo $REPLY
hello

$read answer
hello
$echo $answer
hello

$read first second third
chen xiaopang panda
$echo $first $second $third
chen xiaopang panda

$read -p "Enter your name:" name
Enter your name:chenxiaopang
$echo $name
chenxiaopang

$read -a friends
Tom Mike Jack
$echo ${friends[*]}
Tom Mike Jack

$read -t 5 choice //限定5秒钟内输入变量值，否则，不管用户是否输入，read命令返回非零值

$read -n1 -p 'Enter your Choice (y/n): ' choice
$echo $choice
y

$read -s name

cat test.txt | while read line
do

done?