awk flags & options

-F

Set the field separator. Default is whitespace.

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

awk -F, '{print $2}' data.csv

-v

Set a variable before execution begins.

awk -v threshold=100 '$1 > threshold' data.txt

-f

Read the awk program from a file instead of the command line.

awk -f script.awk data.txt

{print}

Print the entire line, or specific fields ($1, $2, etc.).

awk '{print $1}' file.txt

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

$NF

NF is the number of fields. $NF is the last field on the line.

awk '{print $NF}' file.txt

NR

NR is the current line number. Use it to filter by line.

awk 'NR==5' file.txt

awk 'NR>=10 && NR<=20' file.txt

/pattern/

Process only lines matching a regular expression.

awk '/error/' log.txt

awk '/^[0-9]/' file.txt

BEGIN, END

Run code before the first line or after the last line.

awk 'BEGIN{sum=0} {sum+=$1} END{print sum}' numbers.txt

OFS

Output field separator. Controls what goes between printed fields.

awk -F: -v OFS=, '{print $1, $3}' /etc/passwd

Conditional logic

Use if/else and comparison operators.

awk '{if ($3 > 100) print $1, "high"; else print $1, "low"}' data.txt