sed 不能对空文件进行操作，先创建一个不为空的文件。
cat > test.txt <<EOF
HELLO LINUX!
Linux is a free unix-type opterating system.
This is a linux testfile!
Linux test
newLine
Google
Taobao
Runoob
Tesetfile
Wiki
EOF
1、追加和插入
当前文件只有一行，所以行号只能为1。
[root@VM-16-17-centos 123]# sed -i '1a 222' test.txt
[root@VM-16-17-centos 123]# cat test.txt
HELLO LINUX!
222
Linux is a free unix-type opterating system.
This is a linux testfile!
Linux test
newLine
Google
Taobao
Runoob
Tesetfile
Wiki
[root@VM-16-17-centos 123]# sed -i '1i 000' test.txt
[root@VM-16-17-centos 123]# cat test.txt
000
HELLO LINUX!
222
Linux is a free unix-type opterating system.
This is a linux testfile!
Linux test
newLine
Google
Taobao
Runoob
Tesetfile
Wiki
2、删除
[root@VM-16-17-centos 123]# cat test.txt
000
HELLO LINUX!
222
Linux is a free unix-type opterating system.
This is a linux testfile!
Linux test
newLine
Google
Taobao
Runoob
Tesetfile
Wiki
[root@VM-16-17-centos 123]# sed -i '1,3d' test.txt
[root@VM-16-17-centos 123]# cat test.txt
Linux is a free unix-type opterating system.
This is a linux testfile!
Linux test
newLine
Google
Taobao
Runoob
Tesetfile
Wiki
删除了1-3行。
3、替换
[root@VM-16-17-centos 123]# cat test.txt
HELLO LINUX!
Linux is a free unix-type opterating system.
This is a linux testfile!
Linux test
newLine
Google
Taobao
Runoob
Tesetfile
Wiki
3.1 替换指定行
[root@VM-16-17-centos 123]# sed -i '2s/is/is not/g' test.txt
[root@VM-16-17-centos 123]# cat test.txt
HELLO LINUX!
Linux is not a free unix-type opterating system.
This is a linux testfile!
Linux test
newLine
Google
Taobao
Runoob
Tesetfile
Wiki
只有第二行被替换。
3.2 全局替换
[root@VM-16-17-centos 123]# sed -i 's/is/is not/g' test.txt
[root@VM-16-17-centos 123]# cat test.txt
HELLO LINUX!
Linux is not a free unix-type opterating system.
This not is not a linux testfile!
Linux test
newLine
Google
Taobao
Runoob
Tesetfile
Wiki
第二行和第三行都被替换。
