Mastering the awk Command

What is awk?

awk is a scripting language (command) for efficiently extracting, processing, and aggregating text data in Linux/Unix environments.

Reference: GNU awk

What This Article Covers

This article explains the awk command divided into the following 8 categories:

Conditional Branching & Control Structures
Functions & Processing
String Processing & Regular Expressions
Fields & Records
Arrays & Data Structures
Variables & Scripts
Comparison & Integration with Other Commands
Data Splitting

Each section starts with code and output to verify basic behavior, making it easy to confirm how things work.

Follow the links for more detailed behavior.

Conditional Branching & Control Structures

Basic Syntax of awk if

Create File

cat << 'EOF' > input.txt
apple 100
banana 200
cherry 150
EOF

Command

awk '{ if ($2 > 150) print $1, $2 }' input.txt

Output

banana 200

Details of awk if

A Beginner’s Guide to Text Processing using awk and if

Basic Syntax of awk begin

Create File

cat << 'EOF' > input.txt
apple 100
banana 200
orange 300
EOF

Command

awk 'BEGIN { print "=== Start Processing ===" }
     { print "Item:", $1, "Price:", $2 }
     END { print "=== End Processing ===" }' input.txt

Output

=== Start Processing ===
Item: apple Price: 100
Item: banana Price: 200
Item: orange Price: 300
=== End Processing ===

Details of awk begin

The Ultimate Guide to AWK BEGIN Blocks: From Variable Initialization to Aggregation Patterns

Functions & Processing

Basic Syntax of awk function

Create File

cat << 'EOF' > input.txt
apple 100
banana 200
orange 150
EOF

Command

awk '
function add_tax(price) {
return price * 1.1
}
{
taxed = add_tax($2)
print $1, taxed
}
' input.txt

Output

apple 110
banana 220
orange 165

Details of awk function

A Practical Guide to Understanding awk Functions and Achieving Efficient Text Processing

Basic Syntax of awk printf

Create File

cat << 'EOF' > input.txt
apple 100
banana 200
orange 150
EOF

Command

awk '{printf "%s : %d\n", $1, $2}' input.txt

Output

apple : 100
banana : 200
orange : 150

Details of awk printf

Mastering Data Formatting with awk and printf: A Beginner’s Guide

Basic Syntax of awk getline

Create File

cat << 'EOF' > input.txt
line1
line2
line3
EOF

Command

awk '{
print "Current line:", $0
if (getline next_line) {
print "getline result:", next_line
}
}' input.txt

Output

Current line: line1
getline result: line2
Current line: line3

Details of awk getline

A Practical Guide to Understanding awk getline and Its Safe Usage

String Processing & Regular Expressions

Basic Syntax of awk match

Create File

cat << 'EOF' > input.txt
Hello 123 World
abc456def
no numbers here
EOF

Command

awk '{ if (match($0, /[0-9]+/)) print $0, "-> RSTART=" RSTART ", RLENGTH=" RLENGTH }' input.txt

Output

Hello 123 World -> RSTART=7, RLENGTH=3
abc456def -> RSTART=4, RLENGTH=3

Details of awk match

Mastering awk’s match Function: A Practical Approach

Basic Syntax of awk sub

Create File

cat << 'EOF' > input.txt
apple orange apple
banana apple grape
EOF

Command

awk '{ sub("apple","APPLE"); print }' input.txt

Output

APPLE orange apple
banana APPLE grape

Details of awk sub

Mastering the sub Function in awk: A Beginner’s Guide

Basic Syntax of awk gsub

Create File

cat << 'EOF' > input.txt
apple orange apple grape
EOF

Command

awk '{ gsub("apple", "banana"); print }' input.txt

Output

banana orange banana grape

Details of awk gsub

Mastering awk gsub: A Beginner’s Guide to String Replacement from Basics to Advanced

Basic Syntax of awk substr

Create File

cat << 'EOF' > input.txt
Hello,awk,substr,function
EOF

Command

awk '{ print substr($0,1,5) }' input.txt

Output

Hello

Details of awk substr

Mastering the awk substr Function: A Hands-on Guide

Basic Syntax of awk Regular Expressions

Create File

cat << 'EOF' > input.txt
apple 123
banana 456
cherry_789
grape-001
EOF

Command

awk '/[a-z]+ [0-9]+/' input.txt

Output

apple 123
banana 456

Details of awk Regular Expressions

A Beginner’s Guide to awk and Regular Expressions

Fields & Records

Basic Syntax of awk nf

Create File

cat << 'EOF' > input.txt
apple orange banana
cat dog
red blue green yellow
EOF

Command

awk '{print NF}' input.txt

Output

3
2
4

Details of awk nf

Mastering AWK and NF: The Practical Guide to Seamless Data Processing

Basic Syntax of awk nr

Create File

cat << 'EOF' > input.txt
apple
banana
cherry
EOF

Command

awk '{print NR, $0}' input.txt

Output

1 apple
2 banana
3 cherry

Details of awk nr

Mastering awk: An Introductory Guide to NR and Row Manipulation

Basic Syntax of awk fs

Create File

cat << 'EOF' > input.txt
apple,100,red
banana,200,yellow
grape,300,purple
EOF

Command

awk -F',' '{print $1, $2, $3}' input.txt

Output

apple 100 red
banana 200 yellow
grape 300 purple

Details of awk fs

AWK FS Fundamentals: Essential and Applied Techniques

Basic Syntax of awk ofs

Create File

cat << 'EOF' > input.txt
apple orange banana
dog cat mouse
EOF

Command

awk 'BEGIN{OFS=","} {print $1, $2, $3}' input.txt

Output

apple,orange,banana
dog,cat,mouse

Details of awk ofs

Mastering Delimiters with awk and OFS

Basic Syntax of awk field separator

Create File

cat << 'EOF' > input.txt
apple orange banana
cat dog mouse
one two three
EOF

Command

awk '{print $1, $2, $3}' input.txt

Output

apple orange banana
cat dog mouse
one two three

Details of awk field separator

Mastering awk Fields and Separators: A Practical Introduction

Arrays & Data Structures

Basic Syntax of awk array

Create File

cat << 'EOF' > input.txt
apple 100
banana 200
apple 150
orange 300
banana 50
EOF

Command

awk '{ arr[$1] += $2 } END { for (key in arr) print key, arr[key] }' input.txt

Output

apple 250
banana 250
orange 300

Details of awk array

AWK Arrays: A Beginner’s Guide to the Fundamentals

Variables & Scripts

Basic Syntax of awk variable

Create File

cat << 'EOF' > input.txt
apple 100
banana 200
orange 300
EOF

Command

awk '{ total += $2 } END { print total }' input.txt

Output

Details of awk variable

AWK Variables Explained: A Beginner’s Guide to the Essentials

Basic Syntax of awk script

Create File

cat << 'EOF' > input.txt
apple
banana
cherry
EOF

Create File

cat << 'EOF' > script.awk
BEGIN { print "=== awk script start ===" }
{ print NR ":" $0 }
END { print "=== awk script end ===" }
EOF

Command

awk -f script.awk input.txt

Output

=== awk script start ===
1:apple
2:banana
3:cherry
=== awk script end ===

Details of awk script

Mastering Text Processing: Learning awk and Scripting

Comparison & Integration with Other Commands

Basic Syntax of awk sed

Create File

cat << 'EOF' > input.txt
apple 100
banana 200
orange 300
EOF

Command

awk '{ print $1, $2 }' input.txt

Output

apple 100
banana 200
orange 300

Command

sed 's/ / : /' input.txt

Output

apple : 100
banana : 200
orange : 300

Details of awk sed

Text Processing Basics with awk and sed

Basic Syntax of awk grep

Create File

cat << 'EOF' > input.txt
apple 100
banana 200
orange 150
apple 300
grape 120
EOF

Command

awk '{print $1, $2}' input.txt

Output

apple 100
banana 200
orange 150
apple 300
grape 120

Command

grep "apple" input.txt

Output

apple 100
apple 300

Details of awk grep

Mastering awk and grep: A Practical Foundation Guide

Basic Syntax of awk sort

Create File

cat << 'EOF' > input.txt
apple 300
orange 150
banana 200
grape 180
apple 120
EOF

Command

awk '{ print $1, $2 }' input.txt

Output

apple 300
orange 150
banana 200
grape 180
apple 120

Command

sort input.txt

Output

apple 120
apple 300
banana 200
grape 180
orange 150

Details of awk sort

Mastering awk and sort: A Beginner’s Guide

Data Splitting

Basic Syntax of awk split

Create File

cat << 'EOF' > input.txt
apple,orange,banana
EOF

Command

awk '{
split($0, fruits, ",")
print fruits[1]
print fruits[2]
print fruits[3]
}' input.txt

Output

apple
orange
banana

Details of awk split

Mastering the awk split Function: Explained Simply for New Users

Summary

This article explained the awk command divided into the following 8 categories:

Conditional Branching & Control Structures
Functions & Processing
String Processing & Regular Expressions
Fields & Records
Arrays & Data Structures
Variables & Scripts
Comparison & Integration with Other Commands
Data Splitting

We comprehensively covered awk's fundamental design through advanced text manipulation and integration with other commands, showcasing its powerful data processing capabilities.

awk is not merely a text filter — it is a highly complete "programming language" equipped with control structures, dynamic arrays, and a rich set of built-in functions.

By applying the techniques introduced in each section, you will be able to efficiently handle everyday troubleshooting tasks — such as aggregating bloated logs or performing complex data splits — with a single-line script (one-liner).