awk Command

awk is a powerful text processing language and command for pattern scanning, field extraction, and data transformation. It processes input line by line, splitting each line into fields, making it ideal for working with structured text like CSV files, log files, and command output.

awk programs consist of pattern-action pairs: when a line matches the pattern, the corresponding action executes. The default field separator is whitespace, but it can be changed with -F. Built-in variables like NR (record number), NF (number of fields), and FS (field separator) provide context for processing.

While sed is designed for stream editing (find-and-replace), awk excels at columnar data extraction and computation. It supports variables, arrays, arithmetic, string functions, and control flow — making it a complete programming language for text processing tasks.

Option	Description	Example
-F	Set field separator (default: whitespace)	awk -F',' '{print $1}' data.csv
-v	Assign a variable before execution	awk -v threshold=100 '$3 > threshold' data.txt
-f	Read awk program from a file	awk -f script.awk input.txt
BEGIN	Execute block before processing any input	awk 'BEGIN{print "Header"} {print}' file
END	Execute block after all input is processed	awk '{sum+=$1} END{print sum}' numbers.txt
NR	Built-in variable: current record (line) number	awk 'NR>=10 && NR<=20' file.txt
NF	Built-in variable: number of fields in current record	awk '{print NF}' file.txt
-OFS	Output field separator	awk -F',' -v OFS='\t' '{$1=$1; print}' file.csv