Summarize the use of sed command in Linux

Summary of how to use sed command in linux

sed command in linux:

1 First introduction to sed

The sed editor is called a stream editor. It is different from interactive text editors such as vim. It processes data in the data stream according to commands. The following operations will be performed:

• Read one row of data from the input at a time (repeat this operation until all rows have been read)

• According to Editor command matches data

• Modify the data in the data stream according to the command

• Output the new data to STDOUT (standard output)

The sed command can be entered from the command line or read from a command file.

sed -e script 添加script中指定的命令
sed -f file 添加file中指定的命令

1.1 Define the sed command on the command line [Recommended learning: linux video tutorial]

Let’s look at a simple text replacement example:

echo "hi,my name is xxx" | sed 's/xxx/kinsomy/'
#修改文件
sed 's/xxx/kinsomy/' data.txt
#执行多个命令 用-e选项,分号隔开
sed 's/xxx/kinsomy/; s/***/hhh/' data.txt

Input the data output by echo into sed through the pipeline, and then use the s command to replace the matching data after the first slash with the data after the second slash.

Note: sed operates the data in the text file and only outputs the modified data to STDOUT, but does not modify the data in the file itself

1.2 Reading commands from the file

Define a series of commands in a file script.sed to facilitate reuse.

s/*/a
s/x/b
s/-/+

# -f选项指定命令文件
sed -f script.sed data.txt

2 sed basics

2.1 Replacement tags

The above example echo "hi,my name is xxx" | sed 's/ xxx/kinsomy/' will only replace the first matched data in each row, but if there are multiple matches in a row of data, they cannot all be replaced.

echo "hi,my name is xxx, i am xxx" | sed 's/xxx/kinsomy/'
#输出
hi,my name is kinsomy, i am xxx

At this time, you can use some substitution flags to set the replacement mode. The replacement token follows the replacement string.

s/pattern/replacement/flags

Number, indicating at which matched data will be replaced

echo "hi,my name is xxx, i am xxx" | sed 's/xxx/kinsomy/2'
#输出 第二个xxx被替换成kinsomy
hi,my name is xxx, i am kinsomy

g, indicating replacement of all matched data

echo "hi,my name is xxx, i am xxx" | sed 's/xxx/kinsomy/g'
#输出 第二个xxx被替换成kinsomy
hi,my name is kinsomy, i am kinsomy

p, Indicates that the matched lines will be printed out

echo "hi,my name is xxx, i am xxx" | sed 's/xxx/kinsomy/p'
#输出
hi,my name is kinsomy, i am xxx
hi,my name is kinsomy, i am xxx

w,将替换后输出保存到指定文件
echo "hi,my name is xxx, i am xxx" | sed 's/xxx/kinsomy/w output.txt'

2.3 Line addressing

As mentioned above, the sed command reads text line by line and performs matching operation data until all lines are After traversing, if we want to operate on a specific row at this time, we must use row addressing. There are two forms of line addressing:

The numeric form represents the line

# 操作单行
$ sed '2s/xxx/***/' data.txt
# 操作一定行区间[2,4]
$ sed '2,4s/xxx/***/' data.txt
# 操作某行开始到最后[2,endline]
$ sed '2,$s/xxx/***/' data.txt

Text mode filter

First find the kinsomy record in /etc/passwd, and then Replace bash with csh. Text pattern filters can be very powerful when paired with regular expressions.

sed '/kinsomy/s/bash/csh/' /etc/passwd

2.4 Delete lines

Use the delete command d to delete the text.

# 删除所有文本
sed 'd' data.txt
# 删除单行
sed '2d' data.txt
# 删除行区间[2,3]
sed '2,3d' data.txt
# 删除行区间[2,endline]
sed '2,$d' data.txt
# 删除匹配文本aa的行
sed '/aa/d' data.txt
# 删除两个匹配文本之间的文本 匹配到1和3的行之间的文本全部被删除
sed '/1/,/3/d' data.txt

2.5 Insert and append text

Insert command i adds a new line before the specified line

Append command a adds a new line after the specified line

# 追加
echo "Line 2" | sed 'a\
pipe quote> Line 1'
#插入
echo "Line 2" | sed 'i\
pipe quote> Line 1'

2.6 Modify a line

c command is used to modify a line of data

# 修改第三行文本
sed '3c\
pipe quote> change line ' data.txt

2.7 Conversion command

Command format sed 'y/inchar/outchar'

will Characters in inchar are converted into outchar characters in one-to-one correspondence

echo "This 1 is a test of 1 try." | sed 'y/123/456/'
# 输出
This 4 is a test of 4 try.

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