Adnan al-emran ontor

Posted on Nov 17

AWK Cheat Sheet

What is AWK?

awk is a powerful text-processing tool in Linux used to manipulate and analyze text files by processing patterns and performing actions.

Basic Syntax


awk 'pattern {action}' file

pattern: The condition to match (optional).
action: Commands to execute on matching lines (optional).
file: The file to process.

Common Examples

1. Print All Lines


awk '{print}' file.txt

Outputs all lines in file.txt.

2. Print Specific Columns

 awk '{print $1, $3}' file.txt

Prints the 1st and 3rd columns.

3. Match a Pattern


awk '/error/ {print}' log.txt

Prints lines containing the word error.

4. Conditional Filtering


awk '$3 > 100 {print $1, $3}' data.txt

Prints rows where the 3rd column is greater than 100.

5. Add or Modify Columns


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

Adds a column with the sum of the 2nd and 3rd columns.

6. Count Matching Lines


awk '/pattern/ {count++} END {print count}' file.txt

Counts and prints lines matching pattern.

7. Format Output


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

Formats and prints fields with a custom output.

8. Use Field Separator


awk -F ':' '{print $1, $NF}' /etc/passwd

Uses : as a separator and prints the 1st and last columns.

Key Concepts

Symbol	Meaning
`$1`, `$2`	Represents the 1st, 2nd columns (fields).
`NR`	Line number (e.g., `NR == 5` matches line 5).
`NF`	Total number of fields in a line.
`FS`	Field Separator (`-F` or `FS=","`).
`BEGIN`	Executes before processing lines.
`END`	Executes after processing all lines.

Advanced Examples

Print Line Numbers


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

Prints line numbers alongside the content.

Find Maximum in a Column


awk '$3 > max {max = $3} END {print max}' data.txt

Finds and prints the maximum value in the 3rd column.

Sum a Column


awk '{sum += $3} END {print sum}' data.txt

Sums up all values in the 3rd column.

Filter by Field Count


awk 'NF == 3 {print}' file.txt

Prints lines with exactly 3 fields.

Practice Data

Create a sample.txt to test commands:


John 25 500
Mary 30 600
Alex 28 450

Tips

Test commands with awk on small files before applying to large ones.
Combine with other commands like grep or sed for complex workflows.

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