awk command Guide | How to arrange the output of the file in Linux

Table of Contents

• Introduction to AWK Command
• Syntax of Awk Command
• Full Guide for AWK Command
• Recent Articles on Linux
• Related Articles to Cybersecurity Tools

Introduction to AWK Command

"awk“ command is a powerful text processing tool in Linux and Unix-like operating systems. It allows you to process and manipulate text files based on patterns and actions defined in a program.

The “awk” command is a tool for reporting and data extraction that was created as a domain-specific

language for text processing.

It is a data-driven scripting language made comprised of several operations to be performed on textual data streams, either directly on files or as part of a pipeline, with the goal of extracting and converting data to produce prepared reports.

Syntax of Awk Command

$ awk options 'pattern { action }' file

Let’s break down the components:

• options (optional): You can specify various options to customize the behavior of the awk commands, such as field separators or output formatting.
• pattern (optional): It defines a pattern that specifies which lines or records to match. If omitted, the action block will be executed for all input lines.
• action: This is a set of commands enclosed in curly braces executed for each line or record that matches the pattern. If a pattern is not provided, the action block is executed for every line.
• file: Specifies the input file(s) to be processed. If no file is provided, awk it reads from standard input (e.g., data piped from another command).

Full Guide for AWK Command

Let’s see our data.txt file and what content we have stored in the file.

$ cat data.txt
  
ID  Name  Position  Salary
1   Bob   HR         1000
2   White   Developer 2000
3   Gill    Tester    3000
4   Lara   Tester     4000
5   Sam   Developer   5000

A) Print the specific column of the data.

$ awk '{print $2}' data.txt 

Name
Bob
White
Gill
Lara
Sam

From the above command, we can clearly see that we want to display the second column i.e. Name column, that’s why we have to use $2 in the command.

B) Print multiple columns of the data

$ awk '{print $2,$4}' data.txt 

Name Salary
Bob   1000
White 2000
Gill  3000
Lara  4000
Sam   5000

From the above command, we can clearly see that we want to display multiple columns i.e. 2 and $4, that’s why we have to use $2 and $4 in the command.

C) Print the last column of the data

$ awk '{print $NF}' data.txt

Salary
1000
2000
3000
4000
5000

From the above command, we can clearly see that we have successfully displayed the last column of the data file.

D) Print Specific Columns with Delimeter

$ awk '{print NR ": ", $2}' data.txt 
1:  Name
2:  Bob
3:  White
4:  Gill
5:  Lara
6:  Sam

From the above command, we can clearly see that we have successfully displayed the data in the proper format addition with the colon(:).

E) Remove the delimiter of the data and display the data.

$ cat info.txt 
ID,employee_name,salary
1,sam,3000
2,copper,4000
3,travis,6000

From the above output, we can clear see theoutput of the data but the problem is that it includes the comma which is not easy to understand by the user.

$ awk -F, '{print $2,$3}' info.txt 

employee_name salary
sam 3000
copper 4000
travis 6000

From the above output, we can clear see theoutput of the data in which we clearly see that comma is being remove with the option -F with the comma operator.

F) Condition Based Output with Awk Command

$ cat data.txt 
ID  Name  Position  Salary
1   Bob   HR         1000
2   White   Developer 2000
3   Gill    Tester    3000
4   Lara   Tester     4000
5   Sam   Developer   5000

$ awk '{if($4 > 3000) print $0}' data.txt 
ID  Name  Position  Salary
4   Lara   Tester     4000
5   Sam   Developer   5000

From the above output, we can conclude that the display output have salary greater than 3000, we have achieve that with the help of if condition in the awk command.

F) Update the data with awk Command

$ cat data.txt 
ID  Name  Position  Salary
1   Bob   HR         1000
2   White   Developer 2000
3   Gill    Tester    3000
4   Lara   Tester     4000
5   Sam   Developer   5000

$ awk '{if($2=="Bob") {($4=8000)} print $0}' data.txt 
ID  Name  Position  Salary
1    Bob      HR     8000
2   White   Developer 2000
3   Gill    Tester    3000
4   Lara   Tester     4000
5   Sam   Developer   5000

From the above output, we can conclude that we have update the data of Bob with the salary of 8000.

G) Search and print the specific record

$ cat data.txt 
ID  Name  Position  Salary
1   Bob   HR         1000
2   White   Developer 2000
3   Gill    Tester    3000
4   Lara   Tester     4000
5   Sam   Developer   5000

$ awk '/Tester/ {print $0}' data.txt 
3   Gill    Tester    3000
4   Lara   Tester     4000

From the above output, we can conclude that we have search the term “Tester” and print that records.

H) Print the specific line of the record

$ awk 'NR=="2"{print $0}' data.txt 
1   Bob   HR         1000

From the above output, we have display only the second record.

I) Print the specific range of the line of the record

$ awk 'NR=="2",NR=="4" {print $0}' data.txt 
1   Bob   HR         1000
2   White   Developer 2000
3   Gill    Tester    3000

From the above output, we have display record from range 2 to 4 that means 3 records.

J) Print the number of lines in the record

$ awk 'END {print NR}' data.txt 
6

K) For Loop in awk command

$ awk 'BEGIN {for(i=0;i<10;i++) print i;}'
0
1
2
3
4
5
6
7
8
9

L) While loop in awk command

$ awk 'BEGIN {while(i<10) {i++; print "num is " i}}'
num is 1
num is 2
num is 3
num is 4
num is 5
num is 6
num is 7
num is 8
num is 9
num is 10

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