Shell script text three swordsman awk

Catalog

1 awk Tool is introduced

1.1 working principle

1.2 awk Common built-in variables （ Can be directly used ）

2 example

2.1 Print text content

2.2 awk Arithmetic

 2.2.1 Fuzzy matching , use ~ Means to contain ,!~ Does not include

2.2.2  About the comparison between numeric value and string

2.2.3  Logical operations &&（ And ）、||（ or ）

​2.2.4 Usage of other built-in variables

3 awk Advanced usage

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1 awk Tool is introduced

• AWK Is a language for processing text files , Is a powerful text analysis tool
• Complex text manipulation can be realized in non interactive mode
• Compare with sed It is often used for the processing of an entire line ,awk It is more likely to be divided into several fields in a row , because awk Quite suitable for small text data .

1.1 working principle

When you read the first line , Matching condition , Then perform the specified action , Then read the second line of data processing , No default output . If no matching criteria are defined, the default is to match all data rows ,awk Implicit loop , The action will be executed as many times as the condition matches .

Read the text line by line , The default is space or tab Key to separate the separator , Save the separated fields to the built-in variables , And execute the edit command according to the mode or condition .

sed Commands are often used for a whole line of processing , and awk They tend to divide a line into multiple " Field " And then deal with it .awk Information is also read line by line , The execution result can be obtained through print To print and display field data .

In the use of awk In the course of the order , You can use logical operators “&&” Express “ And ”、“||” Express “ or ”、“！” Express “ Not ”; You can also do simple mathematical operations , Such as +、-、*、/、%、^ Respectively means plus 、 reduce 、 ride 、 except 、 The remainder and the power .

Command format ：

1. awk [ Options ]  ‘ Mode conditions { operation }’  file 1 file 2...
2. awk -f|-v Script files file 1 file .....

1.2 awk Common built-in variables （ Can be directly used ）

• FS∶ Column separator . Specify the field separator for each line of text , Default to space or tab stop . And "-F" The same effect
• NF∶ Number of fields in the row currently processed .
• NR∶ Line number of the currently processed line （ Ordinal number ）.
• $0∶ The entire contents of the currently processed row .
• $n∶ Of the current processing line n A field （ The first n Column ）.
• FILENAME∶ File name processed .
• RS∶ Line separator .awk When reading from a file , Based on the RS The definition of cut data into many records , and awk Read only one record at a time , To deal with . The default is ’\n’. Jane said as ： Data record separation , The default is \n, One record for each action

2 example

2.1 Print text content

example

 

  Expand production ： NIC ip、 Traffic

2.2 awk Arithmetic

Line by line what tasks to perform before starting , What tasks will be performed after the end of , use BEGIN、END
BEGIN Generally used for initialization , Read the data only once before
END It is generally used for summary operation , Execute only once after reading the data record  

example

 2.2.1 Fuzzy matching , use ~ Means to contain ,!~ Does not include

2.2.2  About the comparison between numeric value and string

Comparative symbols ：==      !=       <=       >=      <       >

2.2.3  Logical operations &&（ And ）、||（ or ）

 

2.2.4 Usage of other built-in variables

• FS： Enter the delimiter of the field Default is space
• OFS： Separator for output field The default is also a space
• NR∶ Line number of the currently processed line （ Ordinal number ）
• FNR： Number of records read from the file （ Line number ）, from 1 Start , The new file is redone 1 Start counting
• RS： Enter the line separator   The default is line break
• ORS： Output line separator   The default is line feed  

  example

 

 

3 awk Advanced usage

Call function getline, When reading a row of data, you do not get the current row, but the next row of the current row