sed是一种流编辑器，是一款处理文本比较优秀的工具，可以结合正则表达式一起使用
sed执行过程

sed命令

命令: sed
语法 : sed [选项]... {命令集} [输入文件]...
常用命令:

           d  删除选择的行    
            s   查找    
            y  替换
            i   当前行前面插入一行
            a  当前行后面插入一行
            p  打印行       
            q  退出     

 替换符:

            数字 ：替换第几处    
            g :  全局替换    
            \1:  子串匹配标记，前面搜索可以用元字符集\(..\)
            &:  保留搜索刀的字符用来替换其他字符

操作:
替换

查看文件:

[hzy@hzy ~]$ sed 's/little/big/' word
Twinkle, twinkle, big star
How I wonder what you are
Up above the world so high
Like a diamond in the sky
When the blazing sun is gone

查看文本:

[hzy@hzy ~]$ cat word1
Oh if there's one thing to be taught
it's dreams are made to be caught
and friends can never be bought
Doesn't matter how long it's been
I know you'll always jump in
'Cause we don't know how to quit

全局替换:

[hzy@hzy ~]$ sed 's/to/can/g' word1
Oh if there's one thing can be taught
it's dreams are made can be caught
and friends can never be bought
Doesn't matter how long it's been
I know you'll always jump in
'Cause we don't know how can quit

删除:

查看文本:

[hzy@hzy ~]$ cat word
Twinkle, twinkle, little star
How I wonder what you are
Up above the world so high
Like a diamond in the sky
When the blazing sun is gone

删除:

[hzy@hzy ~]$ sed '2d' word
Twinkle, twinkle, little star
Up above the world so high
Like a diamond in the sky
When the blazing sun is gone

显示行号:

[hzy@hzy ~]$ sed '=;2d' word
1
Twinkle, twinkle, little star
2
3
Up above the world so high
4
Like a diamond in the sky
5
When the blazing sun is gone

删除第2行到第四行:

[hzy@hzy ~]$ sed '=;2,4d' word
1
Twinkle, twinkle, little star
2
3
4
5
When the blazing sun is gone

添加行:
向前插入:

[hzy@hzy ~]$ echo "hello" | sed 'i\kitty'
kitty
hello

向后插入:

[hzy@hzy ~]$ echo "kitty" | sed 'i\hello'
hello
kitty

修改行:

替换第二行为hello kitty

[hzy@hzy ~]$ sed '2c\hello kitty' word
Twinkle, twinkle, little star
hello kitty
Up above the world so high
Like a diamond in the sky
When the blazing sun is gone

替换第二行到最后一行为hello kitty

[hzy@hzy ~]$ sed '2,$c\hello kitty' word
Twinkle, twinkle, little star
hello kitty

写入行

把带star的行写入c文件中,c提前创建

[hzy@hzy ~]$ sed -n '/star/w c' word
[hzy@hzy ~]$ cat c
Twinkle, twinkle, little star

退出

打印3行后，退出sed

[hzy@hzy ~]$ sed '3q' word
Twinkle, twinkle, little star
How I wonder what you are
Up above the world so high