shell:读取文件的每一行内容并输出

写法一：
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#!/bin/bash

while read line
do
    echo $line
done < file(待读取的文件)
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写法二：
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#!/bin/bash

cat file(待读取的文件) | while read line
do
    echo $line
done
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写法三：
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for line in `cat file(待读取的文件)`
do
    echo $line
done
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