Linux Common Commands--awk

awk 一种编程语言

Syntax format: awk "option" ' Pattern{action} ' "File" ... awk [option] ' condition {action} ' [file] ...
Note: There must be at least one space between each element in the awk command and in subsequent options and files
Option Description:

parameter Options	Explanatory notes
-F	Specify character characters delimiter
-V	Define or modify a variable inside the awk
$	Fetch, reference
$	First column
$	Entire row
$NF	Last line
$ (NF-1)	Penultimate line
Rs	Delimiter for each record read in (similar to line break \ n)
Nr	Line number, number of records
ORS	Delimiter for output time

Relational operators

operator	meaning	Example
<	Less than	X < y
<=	Less than or equal	X <= y
==	Equals	x = = y
!=	Not equal to	X! = y
>=	Less than	X < y
<	Greater than or equal	X >= y
>	Greater than	X > Y
~	Match Regular expression	x~/y/
!~	does not match the regular expression	X!~y

Case one:
Introduction to the AWK environment

Case TWO:
awk Execution Process:

1. awk reads the first line of content
2. to determine whether the conditions in the pattern are met (for example: nr>=2)
   A. If the match executes the corresponding action (e.g. {print $})
   B. If the condition is not matched, continue reading the next line
li> continue to the next line
3. Repeat procedure 1-3, know the last line read (Eof:end of file)

   Simple description of the record:

4. How many steps does an elephant put in a refrigerator? Open the refrigerator door, put the elephant in, close the refrigerator door.
5. to debug your awk command with NR, NF, $ number.
6. NR holds the number of each record (line number) when the new line is read automatically +1
7. RS is the delimiter for the record, and a simple understanding is that you can specify the end flag for each record.
8. use RS instead of \ n
9. rs action means the end of a record
10. FS marks the end of each zone

    AWK basic structure
    awk begin{coms}/pattern/{ COMs} end{coms}
    Start the module,/Who/{to do}, End module

11. begin and end modules can only have one, begin{}begin{} or end{}end{}
12. who does the module? can have multiple (for example: Nr==2{print $ nr==5{print)
    Case three:
    parameter Rs,nr example
    
    
    Description: When RS is null, print the output record number in the line hand and print out each row The contents of the
    Regular expression Simple example
    
    Note: $1~ indicates a match to the first column (the first region), o{1,2} indicates that the condition has one or two o,{print nr,$1,nf} for printing line numbers, first column, last column
    Case FOUR:
    Use awk to remove the corresponding port number,
    
    The number of empty lines in the statistics file
    
    New file, with a space delimiter, area 3 greater than 15, how many lines
    
    
    
    Use AWK implements a value of 1 and 100
    

Linux common Commands--awk