shell读取文件每一行的方式

while read myline
do
 echo "LINE:"$myline
done < datafile.txt

cat datafile.txt | while read myline
do 
 echo "LINE:"$myline
done

cat datafile.txt | while myline=$(line)
do 
 echo "LINE:"$myline
done

while myline=$(line)
do 
 echo "LINE:"$myline
done < datafile.txt

cat datafile.txt | while read paraa parab parac
do
 echo "PARAA:"$paraa
 echo "PARAB:"$parab
 echo "PARAC:"$parac
done

while read paraa parab parac
do
 echo "PARAA:"$paraa
 echo "PARAB:"$parab
 echo "PARAC:"$parac
done < datafile.txt