shell按行读取文件的3种方法

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

#!/bin/bash
cat filename(待读取的文件) | while read line
do
echo $line
done

for line in `cat filename(待读取的文件)`
do
echo $line
done

$ 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