Linux学习笔记：sed
sed命令
基于行的操作，对STDIN的数据进行替换、删除、新增等操作
参数如下
-n 安静模式。默认情况下，sed会输出所有内容，包括了修改和未修改的内容。使用-n则只输出修改过的那一行内容。
-r 支持扩展正则表达式
-i 直接修改文件，不输出内容
参数-i 直接对文件操作，不会输出任何内容。
sed -i '$aEND LINE' regular_express.txt
$是最后一行的意思，用于指定范围。a则是插入动作。END LINE是一行内容
[root@vmtest ~]# cat regular_express.txt
"Open Source" is a good mechanism to develop programs.
apple is my favorite food.
……
gNu
END LINE
行范围
n1,n2 可选，指定sed的动作只针对从n1行到n2
动作
a 新增，在范围内的每一行下添加一行内容，例子
[root@vmtest ~]# cat -n regular_express.txt |sed '1,3aNew line'
1 "Open Source" is a good mechanism to develop programs.
New line
2 apple is my favorite food.
New line
3 Football game is not use feet only.
New line
4 this dress doesn't fit me.
5 However, this dress is about $ 3183 dollars.
6 GNU is free air not free beer.
7 Her hair is very beauty.
8 I can't finish the test.
范围设置在第1到3行，每一行下方插入一行内容New Line
c 替换，如果有指定范围，则把整个范围替换成一行指定的内容；如果不指定范围，则把STDIN的每一行替换成指定内容。
[root@vmtest ~]# cat -n regular_express.txt |sed '1,3cReplace line'
Replace line
4 this dress doesn't fit me.
5 However, this dress is about $ 3183 dollars.
6 GNU is free air not free beer.
7 Her hair is very beauty
……
可以看到第1-3行被替换成一行
[root@vmtest ~]# cat -n regular_express.txt |sed 'cReplace line'
Replace line
Replace line
Replace line
Replace line
……
每一行都被替换
d 删除，根据条件，删除整行
先看未处理的文件内容
[root@vmtest ~]# cat -n regular_express.txt
1 "Open Source" is a good mechanism to develop programs.
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.
6 GNU is free air not free beer.
[root@vmtest ~]# cat -n regular_express.txt |sed '/3/d'
1 "Open Source" is a good mechanism to develop programs.
2 apple is my favorite food.
4 this dress doesn't fit me.
6 GNU is free air not free beer.
/与/之间是正则条件，只有那行的内容里包含有3这个字符，则整行删除。在原来的内容里第三行包含了行号3，而第5行里包含了$ 3183，所以着两行被删掉了。
另外，如果只指定范围，则把范围的内容删除
[root@vmtest ~]# cat -n regular_express.txt |sed '1,4d'
5 However, this dress is about $ 3183 dollars.
6 GNU is free air not free beer.
但貌似范围与条件不能合着来删除，
i 插入，与a相似，不过a是在原有行下插入一行，而i则是在原有行前插入。
p 打印，配合-n安静模式参数，和范围，可轻松实现打印文件的指定行范围内容
[root@vmtest ~]# cat -n 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.
s///g 替换，如配合范围使用则在范围内替换。
[root@vmtest ~]# cat -n regular_express.txt |sed 's/good/------------/g'
1 "Open Source" is a ------------ mechanism to develop programs.
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.
6 GNU is free air not free beer.
7 Her hair is very beauty.
8 I can't finish the test.
9 Oh! The soup taste ------------.
10 motorcycle is cheap than car.