linux shell 按行循环读入文件方法

linux  shell 按行循环读入文件常用代码如下：

#/bin/bash

printf "*************************************\n"
echo " cat file whiel read line"
cat test.txt |while read line
do
  echo $line;
done

printf "*************************************\n"
echo "while read line <file"
while read line
do
  echo $line;
done <test.txt

printf "*************************************\n"
echo "for line in cat test.txt"
SAVEIFS=$IFS
IFS=$(echo -en "\n")
for line in $(cat test.txt)
do
  echo  $line;
done
IFS=$SAVEIFS

注意：for line in $(cat test.txt)   当文件中有空格或者tab 时，一定要设置一下IFS变量。