shell script text three musketeers sed

1. Sed editor

1.1 Overview of sed

• The sed editor is a stream editor that edits the data stream based on a pre-provided set of rules before the editor processes the data.
• The sed editor can process data in a data stream according to commands, which are either entered from the command line or stored in a command text file.

1.2sed workflow

The sed workflow mainly includes three processes of reading, executing and displaying:

• Read: sed reads a line from the input stream (file, pipe, standard input) and stores it in a temporary buffer (also known as the pattern space)
• Execution: By default, all sed commands are executed sequentially in the pattern space. Unless a line address is specified, the sed command will be executed sequentially on all lines
• Display: Send the modified content to the output stream. After sending the data, the pattern space will be cleared

1.3 sed basic law

sed -e '操作' 文件1 文件2
 
sed -n -e '操作' 文件1 文件2 
 
sed -f 脚本文件 文件1 文件2 
 
sed -i -e '操作' 文件1 文件2

1.4 sed common options

 -e或--expression=多点编辑
 -f或--file=：表示用指定的脚本文件来处理输入的文件
 -h或--help：显示帮助
 -n：不输出模式空间内容到屏幕，即不自动打印，加p，又恢复自动打印
 -i：备份文件并原处编辑
 -r：使用扩展正则表达式

1.5Common operations of sed command

   s：替换，替换指定符。
   d：删除，删除选定的行
   a：增加，在当前行下面增加一行指定内容
   i:插入，在选定的行上面插入一行指定内容
   c：替换，将选定行替换为指定内容
   Y:字符转换，转换前后的字符长度必须相同
   p:打印，如果同时指定行，表示打印指定行，如果不指定行，则表示打印所有内容，如果有非打印字符，则以ascll码输出。其中通常与_n选项一起使用
   =：打印行号
   l：打印数据流中的文本和不可打印的	ASCLL字符（比如结束符s，制表符\t）\

2. Use of sed command

2.1 Print content

• sed' 'input a line in interactive mode and automatically print the same line
• sed -n ' 'Enter a line in interactive mode, turn off automatic printing

Example 1: Print all content

Example 2: View the file and print all the content

Example 3: Print the content of the specified line

Example 4: According to the address, print the specified multi-line content

Example 5: Exit after printing multiple lines

Example 6: Print the last line, using wildcard $

Example 7: Support for regular expressions

Example 8: Filter keywords

Example 9: Keyword Lookup

Example 10: Print odd and even lines of text

2.2 Deleting content

Example 1: Delete the specified row

Example 2: Delete specified multiple lines

Example 3: Delete empty lines in a file

Example 4: Delete the line at the end of the specified character and negate it

Example 5: Back up content before deleting

2.3 Insert content

Example 1: Insert after specified row

Example 2: Insert a blank line, modify the newline of the file, and add a \

Example 3: Replace

2.4 Reconciliation

2.5 Search Alternatives

格式：sed   行范围 s/旧字符串/新字符串/替换标记

Replace tags:

• Number: Indicates which matching place the new string will replace
• g: Indicates that the new string will replace all matching places
• p: print lines matching the substitution command, used with -n
• w file: write the replacement result to the file

Example 1: Modify the configuration file of selinux booting without self-starting

[root@yxp opt]#sed -i 's/SELINUX=enabled/SELINUX=disabled/' /etc/selinux/config 

Example 2: Modify multiple lines, use r and -e

[root@yxp opt]#sed -ri -e 's/SELINUX=disabled/SELINUX=enabled/' /etc/selinux/config  -e 's/SELINUXTYPE=targeted/SELINUXTYPE=111/' /etc/selinux/config 

Example 3; modify the global, followed by g

[root@yxp opt]#sed -i 's/root/admin/g' passwd 

2.6 Group call

Example 1:

Example 2: Extract IP address

[root@yxp ~]#ifconfig ens33 |sed -rn '2s/.*(inet) ([0-9.]+)  (netmask) ([0-9.]+)  (broadcast) ([0-9.]+).*/\2/p'
192.168.59.102

Example 3: @ and / have the same effect