总结

正确的修改进文件命令(替换文件内容)：
sed -i "s#machangwei#mcw#g" mcw.txt

正确的修改追加进文件命令(追加文件内容)：
sed -i "\$a 8: wo bu hao\!" mcw.txt
sed -i '$a 7: wo hen hao!' mcw.txt

最后一行$a追加内容，加上-i修改到文件；单引号无需转义，双引号需要注意特殊字符转义
只有-i和替换，没有-n和打印，才是我们经常需要的替换。将文件内容替换并写入到文件了
第几行上面插入字符串，但是并不修改原文件，加上-i也不行，使用单双引号也不行
匹配指定行上面插入或追加字符串，会报错，加上-i不行，不加还是不行，

替换文件存在的坑

sed -i "s#machangwei#mcw#g" mcw.txt
只有-i和替换，没有-n和打印，才是我们经常需要的替换。将文件内容替换并写入到文件了。不能添加-n和打印做sed替换

 

替换实操

首先创建一个测试文件
[machangwei@mxxx01 ~/mcw]$ mkdir mcw03
[machangwei@mxxx01 ~/mcw]$ cd mcw03/
[machangwei@mxxx01 ~/mcw/mcw03]$ vim mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi machangwei
4: 22bc
5: fff abc
6: abc
[machangwei@mxxx01 ~/mcw/mcw03]$ cp mcw.txt mcw.txt.bak
[machangwei@mxxx01 ~/mcw/mcw03]$ ls
mcw.txt mcw.txt.bak

-n却没有打印，不显示替换结果也不改变文件
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -n "s#machangwei#mcw#g" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi machangwei
4: 22bc
5: fff abc
6: abc

-n没有打印，就是空内容，加上-i就把空内容加到文件里了。文件就空了，内容被删除。sed操作前最好先备份
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -ni "s#machangwei#mcw#g" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$
[machangwei@mxxx01 ~/mcw/mcw03]$ cp mcw.txt.bak mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -ni "s#machangwei#mcw#g" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cp mcw.txt.bak mcw.txt

-n且打印，就显示替换后的那一行，
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -n "s#machangwei#mcw#gp" mcw.txt
3: wo shi mcw

没有-n，替换然后打印。替换的行是重复打印
[machangwei@mxxx01 ~/mcw/mcw03]$ sed "s#machangwei#mcw#gp" mcw.txt
1: ni hao ya
2:
3: wo shi mcw
3: wo shi mcw
4: 22bc
5: fff abc
6: abc

-n加打印p,只显示替换的行，并且显示是替换后的结果
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -n "s#machangwei#mcw#gp" mcw.txt
3: wo shi mcw

-n加打印p,本来就显示替换后的行，加个-i修改文件，那么把显示的替换都的行写入文件，相当于重写文件或者说把显示结果覆盖到原文件
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -ni "s#machangwei#mcw#gp" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
3: wo shi mcw
[machangwei@mxxx01 ~/mcw/mcw03]$ cp mcw.txt mcw.txt.bak
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -n "s#machangwei#mgp" mcw.txt
sed：-e 表达式 #1，字符 16：未终止的“s”命令
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -n "s#machangwei#mcw#gp" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
3: wo shi mcw
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt.bak
3: wo shi mcw

-i插入，后面还有个p打印，会将替换掉的行重复写入到文件
[machangwei@mxxx01 ~/mcw/mcw03]$ vim mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ vim mcw.txt.bak
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -n "s#machangwei#mcw#gp" mcw.txt
3: wo shi mcw
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i "s#machangwei#mcw#gp" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
3: wo shi mcw
4: 22bc
5: fff abc
6: abc

 

[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt.bak
1: ni hao ya
2:
3: wo shi machangwei
4: 22bc
5: fff abc
6: abc
[machangwei@mxxx01 ~/mcw/mcw03]$ cp mcw.txt.bak mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i "s#machangwei#mcw#gp" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
3: wo shi mcw
4: 22bc
5: fff abc
6: abc

只有-i和替换，没有-n和打印，才是我们经常需要的替换。将文件内容替换并写入到文件 了
[machangwei@mxxx01 ~/mcw/mcw03]$ cp mcw.txt.bak mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i "s#machangwei#mcw#g" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
[machangwei@mxxx01 ~/mcw/mcw03]$
[machangwei@mxxx01 ~/mcw/mcw03]$ #上面是替换中存在的坑

追加到文件最后一行实操

准备文件
[machangwei@mxxx01 ~/mcw/mcw03]$ #下面是插入和追加到文件
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc

最后一行追加内容，不加-i会显示追加后的内容，但是不修改文件。这里是单引号
[machangwei@mxxx01 ~/mcw/mcw03]$ sed '$a 7: wo hen hao!' mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc

最后一行追加内容，加上-i修改到文件。这里单引号
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i '$a 7: wo hen hao!' mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!

[machangwei@mxxx01 ~/mcw/mcw03]$ sed "\$a 8: wo bu hao!" mcw.txt
-bash: !": event not found
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i '$a 7: wo hen hao\!' mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ vim mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$

双引号最后一行追加，需要将里面的特殊字符串转义 。不加-i不修改文件
[machangwei@mxxx01 ~/mcw/mcw03]$ sed "\$a 8: wo bu hao\!" mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ #双引号里特殊字符会被解析，所以要转义
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!

双引号最后一行追加，需要将里面的特殊字符串转义 。加-i修改了原文件
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i "\$a 8: wo bu hao\!" mcw.txt
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ sed "$d" mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!

第几行插入字符串，但是并不修改原文件
[machangwei@mxxx01 ~/mcw/mcw03]$ sed '7i 小马过河' mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
小马过河
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!

第几行插入字符串，但是并不修改原文件，加上-i也不行
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i '7i 小马过河' mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
-i 小马过河
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ sed '7i 小马过河' mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
-i i 过河
7: wo hen hao!
8: wo bu hao!

第几行上面插入字符串，但是并不修改原文件，加上-i也不行使用双引号也不行
[machangwei@mxxx01 ~/mcw/mcw03]$ sed "7i 小马过河" mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
小马过河
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i "7i 小马过河" mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
-i 小马过河
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!

匹配指定行上面插入字符串，但是并不修改原文件，加上-i也不行，使用双引号也不行，
[machangwei@mxxx01 ~/mcw/mcw03]$ sed "/wo he/i 小马过河" mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
-i/wo he/i马过河
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03sed '/wo he/i 小马过河' mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
小马过河
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$
[machangwei@mxxx01 ~/mcw/mcw03]$ sed '/wo he/i 小马过河' mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
小马过河
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!

匹配指定行上面插入或追加字符串，会报错，加上-i不行，不加还是不行，
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i '/wo he/i 小马过河' mcw.txt
> ^C
[machangwei@mxxx01 ~/mcw/mcw03]$ sed '/abc/a 小马过河' mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
小马过河
6: abc
小马过河
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ sed -i '/abc/a 小马过河' mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!
[machangwei@mxxx01 ~/mcw/mcw03]$ cat mcw.txt
1: ni hao ya
2:
3: wo shi mcw
4: 22bc
5: fff abc
6: abc
7: wo hen hao!
8: wo bu hao!