sed是一个管道命令，可以分析standard,input;sed也可以将数据进行替换，删除，新增，选取特定行等功能
sed [-nefr] [动作]
-n :经过sed特殊处理的那一行或操作才会被列出来
-e : 直接在命令模式上进行sed动作编辑
以行为单位的新增/删除功能
在第二行后加上add a row字样
[root@izwz9hpp9gmzo5x5e06iqjz home]# nl regular_express.txt |sed '2a add a row'
1 "Open Source" is a good mechanism to develop programs.
2 apple is my favorite food.
add a row
3 Football game is not use feet only.
删除2-5行
[root@izwz9hpp9gmzo5x5e06iqjz home]# nl regular_express.txt |sed 2,5d
1 "Open Source" is a good mechanism to develop programs.
6 GNU is free air not free beer.
7 Her hair is very beauty.
以行为单位的替换与显示功能
第2-5行的内容替换为no 2-5 row
[root@izwz9hpp9gmzo5x5e06iqjz home]# nl regular_express.txt | sed '2,5c no 2-5 row'
1 "Open Source" is a good mechanism to develop programs.
no 2-5 row
6 GNU is free air not free beer.
打印2-5行内容
[root@izwz9hpp9gmzo5x5e06iqjz home]# nl regular_express.txt |sed -n '2,5p'
2 apple is my favorite food.
3 Football game is not use feet only.
4 this dress doesn't fit me.
5 However, this dress is about $ 3183 dollars.
sed 's/要被替换的字符串/新的字符串/g'
直接修改文件内容（危险操作）
sed -i 's/要被替换的字符串/新的字符串/g'
