shell:for和while用法

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：（并发脚本慎用，grep不能输出全部匹配的信息）

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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 fff ggg

cccc dddd

$ cat file | while read line; do echo $line; done

aaaa

bbbb fff ggg

cccc dddd

$ for line in $(<file); do echo $line; done

aaaa

bbbb

fff

ggg

cccc

dddd