假设读取的文件为当期目录下的 test.txt 文件，内容如下：

Google 
Runoob
Taobao

实例 1

#!/bin/bash

while read line
do
    echo $line
done < test.txt

执行输出结果为：

Google
Runoob
Taobao

实例 2

#!/bin/bash

cat test.txt | while read line
do
    echo $line
done

执行输出结果为：

Google
Runoob
Taobao

实例 3

for line in `cat  test.txt`
do
    echo $line
done

执行输出结果为：

Google
Runoob
Taobao

for 逐行读和 while 逐行读是有区别的，如:

$ cat test.txt
Google
Runoob
Taobao

$ cat test.txt | while read line; do echo $line; done
Google
Runoob
Taobao


$ for line in $(<test.txt); do echo $line; done
Google
Runoob
Taobao