#!/bin/bash
bak=$IFS                     #定义一个变量bak保存IFS的值
if [ $# -ne 1 ];then             #判断位置参数是否为1
  echo "Usage $0 filename"
  exit
fi
if [ ! -f $1 ];then               #判断位置参数是否为文件
  echo "the $1 is not a file"
  exit
fi 
IFS=$'\n'                    #将环境变量IFS的值修改为换行符
for i in `cat $1`                #逐行读取文件内容并打印到屏幕
do
  echo $i
done
IFS=$bak                    #将环境变量IFS的值改回原值

#!/bin/bash
if [ $# -ne 1 ];then
  echo "Usage $0 filename"
  exit
fi
if [ ! -f $1 ];then
  echo "the $1 is not a file"
  exit
fi
for i in `cat $1`
do
  echo $i
done

#!/bin/bash
if [ $# -ne 1 ];then             #判断脚本参数是否为1
 echo "Usage:$0 filename"
 exit 1
fi
file=$1                      #将脚本参数参数赋值给变量file
{                            #定义代码块，大括号{}中的代码即为代码块
 read line1 
 read line2
} <$file                       #使用$file将代码块的标准输入指向文件$file
echo "first line in $file is $line1"   #输出文件内容
echo "second line in $file is $line2"
exit 2

#!/bin/bash
if [ $# -ne 1 ];then
 echo "Usage:$0 filename"
 exit 1
fi
file=$1
if [ ! -f $file ];then
 echo "the $file is not a file"
 exit 2
fi
count=0
while read line   #使用read命令循环读取文件内容，并将读取的文件内容赋值给变量line
do
  let count++
  echo "$count $line"
done <$file      #“done <$file”将整个while循环的标准输入指向文件$file
echo -e "\ntotle $count lines read"
exit 0