Done after a while loop in the shell followed by a redirect <

How to read a file:

First step: Pass the contents of the file to the while by pipe (|) or redirect (<)

The second step is to call read in the while and read the contents of the file one line at a time and pay the value to the variable following read. The contents of the current row are saved in the variable.

For example, read file/sites/linuxpig.com.txt

1) How to pipe:

 cat /sites/linuxpig.com.txt |while read LINE do     echo $LINE done当然也可以将cat /sites/linuxpig.com.txt 写成一些复杂一些的，比如：示例1：find -type f -name "*.txt" -exec cat |while read LINE do     echo $LINE done可以将当前目录所有以 .txt 结尾的文件读出示例2：grep -r "linuxpig.com" ./ | awk -F":" ‘{print $1}‘ | cat |while read LINE do     echo $LINE done可以将含有 "linuxpig.com" 字符串的所有文件打开并读取。。示例没有实际测试，如果使用请先测试。。。。。:-)

2) How to redirect:

2.1 using redirects <

 while read LINE do     echo $LINE done < /sites/linuxpig.com.txt

2.2 Using file descriptors (0~9) and redirects <

 exec 3<&0 #先将文件描述符0复制到文件描述符3，也就是给文件描述符0做个备份 exec 0</sites/linuxpig.com.txt  #读文件到文件描述符0 while read LINE # 此变量是读来自stdin（即描述符0）的数据 do     echo $LINE done exec 0<&3 #将文件描述符3复制给文件描述符0（恢复0从键盘读入）

Done after a while loop in the shell followed by a redirect <