shell读取文件的每一行

写法一：
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#!/bin/bash
 
while read line
do
    echo $line
done < filename(待读取的文件)
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写法二：
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#!/bin/bash
 
cat filename(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 filename(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
1111
2222
3333 4444 555
 
$ cat file | while read line; do echo $line; done
1111
2222
3333 4444 555
 
$ for line in $(<file); do echo $line; done
1111
2222
3333
4444
555