个人学习笔记--sed命令（进阶篇）

删除所有空行
[qs@qs ~]$ cat data1
This is the header line.

This is a data line.

This is the last line.
[qs@qs ~]$ sed '/^$/d' data1
This is the header line.
This is a data line.
This is the last line.
[qs@qs ~]$

删除特定空行
[qs@qs ~]$ sed '/header/{n;d}' data1
This is the header line.
This is a data line.

This is the last line.
[qs@qs ~]$ #n命令将会是得sed编辑器移动到模式匹配到的行的下一行。（“下一行”的数据将进入占据模式空间）

-------

[qs@qs ~]$ cat data2
This is the header line.
This is the first data line.
This is the second data line.
This is the last line.
[qs@qs ~]$ sed '/first/{N;s/\n/ /}' data2 #合并行,将模式匹配到的行的下一行合并到模式匹配到的行。（“合并后的行”将占据模式空间）
This is the header line.
This is the first data line. This is the second data line.
This is the last line.
[qs@qs ~]$

[qs@qs ~]$ sed '/first/{N}' data2 #虽然看起来是两行，但是sed编辑器会将它们看成是一行。
This is the header line.
This is the first data line.
This is the second data line.
This is the last line.

[qs@qs ~]$ sed '/first/{N;d}' data2 #证明确实是一行。
This is the header line.
This is the last line.
[qs@qs ~]$

------

[qs@qs ~]$ cat data3
The first meeting of the Linux System
Administrator's group will be held on Tuesday.
All System Administrators should attend this meeting.
Thank you for your attendence.

[qs@qs ~]$ sed 's/System Administrator/Desktop User/' data3 #错误匹配
The first meeting of the Linux System #此处没有匹配到
Administrator's group will be held on Tuesday.
All Desktop Users should attend this meeting. #此处匹配成功
Thank you for your attendence.
[qs@qs ~]$

[qs@qs ~]$ sed 'N; s/System.Administrator/Desktop User/' data3 #正确匹配之一（两行合并）
The first meeting of the Linux Desktop User's group will be held on Tuesday.
All Desktop Users should attend this meeting.
Thank you for your attendence.
[qs@qs ~]$ #System 和 Administrator 之间用了通配符来匹配空格和换行。

[qs@qs ~]$ sed '
> s/System Administrator/Desktop User/
> N
> s/System\nAdministrator/Desktop\nUser/
> ' data3 #正确匹配之二（行不合并，保留原来格式） （注意区分这个和下面的错误示例）
The first meeting of the Linux Desktop
User's group will be held on Tuesday.
All Desktop Users should attend this meeting.
Thank you for your attendence.
[qs@qs ~]$

[qs@qs ~]$ sed '
N
s/System\nAdministrator/Desktop\nUser/
s/System Administrator/Desktop User/
' data4 #错误示例
The first meeting of the Linux Desktop
User's group will be held on Tuesday.
All System Administrators should attend this meeting.
[qs@qs ~]$
这个脚本总是在执行sed编辑器命令之前将下一行文本读入到模式空间。
当读取到最后一行的时候，因为没有下一行，所以N命令就会让sed编辑器停止。

-------
多行删除命令

[qs@qs ~]$ cat data4
The first meeting of the Linux System
Administrator's group will be held on Tuesday.
All System Administrators should attend this meeting.
[qs@qs ~]$ sed 'N; /System\nAdministrator/d' data4 #两行都被删除了
All System Administrators should attend this meeting.
[qs@qs ~]$

[qs@qs ~]$ cat data4
The first meeting of the Linux System
Administrator's group will be held on Tuesday.
All System Administrators should attend this meeting.
[qs@qs ~]$ sed 'N; /System\nAdministrator/D' data4 #多行删除命令D，只删除模式空间的第一行。
Administrator's group will be held on Tuesday.
All System Administrators should attend this meeting.
[qs@qs ~]$

-----

[qs@qs ~]$ cat data9 #第一行是空行

This is the header line.
This is a data line.

This is the last line.
[qs@qs ~]$
[qs@qs ~]$ sed '/^$/{N; /header/D}' data9 #删除从中找到数据字符串的那行的前一行
This is the header line.
This is a data line.

This is the last line.
[qs@qs ~]$

-------

模式空间和保持空间

[qs@qs ~]$ cat data2
This is the header line.
This is the first data line.
This is the second data line.
This is the last line.
[qs@qs ~]$ sed -n '/first/{ #过滤含first的行
> h #当含有first的行出现时，h命令将该行放到保持空间(This is the first data line.)
> p #p命令打印模式空间也就是第一个数据行的内容
> n #n命令提取数据流的下一行（This is the second data line.）, 并将它放到模式空间
> p #p命令打印模式空间的内容，现在是第二个数据行(This is the second data line.)
> g #g命令将保持空间的内容（This is the first data line.）放回模式空间，替换当前文本
> p #p命令打印模式空间的内容（This is the first data line.）
> }' data2
This is the first data line.
This is the second data line.
This is the first data line.
[qs@qs ~]$

-------

排除命令（！）
[qs@qs ~]$ cat data2
This is the header line.
This is the first data line.
This is the second data line.
This is the last line.
[qs@qs ~]$ sed -n '/header/!p' data2 #打印不包含header的行
This is the first data line.
This is the second data line.
This is the last line.
[qs@qs ~]$
-------
[qs@qs ~]$ cat data4
The first meeting of the Linux System
Administrator's group will be held on Tuesday.
All System Administrators should attend this meeting.

[qs@qs ~]$ sed 'N; s/System.Administrator/Desktop User/' data4 #sed编辑器不处理数据流中最后一行文本，因为后面没有其他行了。
The first meeting of the Linux Desktop User's group will be held on Tuesday.
All System Administrators should attend this meeting.

[qs@qs ~]$ sed '$!N; s/System.Administrator/Desktop User/' data4 #最后一行的时候没有执行N命令，其他的都执行了。
The first meeting of the Linux Desktop User's group will be held on Tuesday.
All Desktop Users should attend this meeting.
[qs@qs ~]$
-------
[qs@qs ~]$ cat data2
This is the header line.
This is the first data line.
This is the second data line.
This is the last line.
[qs@qs ~]$
[qs@qs ~]$ sed -n '{1!G; h; $p}' data2 #翻转文本内容
This is the last line.
This is the second data line.
This is the first data line.
This is the header line.
[qs@qs ~]$
-------
[qs@qs ~]$ sed 'G' data2 #加倍行间距（最后一行也加了空行）
This is the header line.

This is the first data line.

This is the second data line.

This is the last line.

[qs@qs ~]$
-------
[qs@qs ~]$ sed '$!G' data2 #最后一行后面不加空行
This is the header line.

This is the first data line.

This is the second data line.

This is the last line.
[qs@qs ~]$
-------
[qs@qs ~]$ cat data9

This is the header line.
This is a data line.

This is the last line.
[qs@qs ~]$
[qs@qs ~]$ sed '/./,$!d' data9 #删除开头的空白行
This is the header line.
This is a data line.

This is the last line.
[qs@qs ~]$
-------
[qs@qs ~]$ cat data10
This is the first line.

This is the second line.

This is the third line.

This is the forth line.
[qs@qs ~]$ sed '/./,/^$/!d' data10 #删除连续的空白行
This is the first line.

This is the second line.

This is the third line.

This is the forth line.
[qs@qs ~]$
-------
[qs@qs ~]$ sed '=' data2 | sed 'N; s/\n/ /' #给文件中的行编号
1 This is the header line.
2 This is the first data line.
3 This is the second data line.
4 This is the last line.
[qs@qs ~]$