bash逐行读取文件内容

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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说明：
for逐行读和while逐行读是有区别的,如:
$ cat file
aaaa
bbbb
cccc dddd

$ cat file | while read line; do echo $line; done
aaaa
bbbb
cccc dddd

$ for line in $(<file); do echo $line; done
aaaa
bbbb
cccc
dddd