awk Cheatsheet - Linux Text Processing Reference

awk's killer use case is column-based aggregation: computing response-code proportions from an nginx log or summing and grouping a report is much faster than writing a script. Understanding RS/FS, NR/NF, and how variables print covers about eighty percent of awk.

SysOps·37 commands·Last updated 2026-07-21

Basic Syntax 6

awk '{print $1}' file

Print the first column (space-separated by default)

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

Use colon as the field separator

awk '{print $1, $NF}' file

Print first and last column

awk '{print NR, $0}' file

Print line number and whole line

awk 'NR==10' file

Print line 10

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

Print lines 10-20

Built-in Variables 8

$0

The whole line

$1, $2, $NF

1st / 2nd / last column

NR

Current line number (global)

NF

Number of columns in the current line

FS

Input field separator (space by default)

OFS

Output field separator

RS

Input record separator (newline by default)

ORS

Output record separator

Conditionals 6

awk '$3 > 100' file

Print lines where column 3 > 100

awk '$1 == \"error\"' file

Print lines where column 1 equals 'error'

awk '$1 ~ /pattern/' file

Column 1 matches a regex

awk '$1 !~ /pattern/' file

Column 1 does not match a regex

awk 'NR==1 || $1 > 100' file

First line or column 1 > 100

awk '$1 == \"a\" {print $2}' file

Condition with action

Statistics 5

awk '{sum += $1} END {print sum}' file

Sum column 1

awk '{sum += $1} END {print sum/NR}' file

Average of column 1

awk '{count++} END {print count}' file

Count lines

awk '{count[$1]++} END {for(k in count) print k, count[k]}' file

Group and count by column 1

awk 'BEGIN{max=0} {if($1>max) max=$1} END{print max}' file

Find the max of column 1

String Functions 7

length($0)

Length of the current line

substr($0, 5, 10)

Substring from char 5, length 10

index($0, \"text\")

Find substring position (1-based; 0 if not found)

split($0, arr, \":\")

Split into an array by a delimiter

sub(/old/, \"new\", $0)

Replace first match

gsub(/old/, \"new\", $0)

Replace all matches

tolower($0) / toupper($0)

Convert to lower/upper case

Common Patterns 5

awk '{print $1}' access.log | sort | uniq -c | sort -rn

Top IPs by access count

awk '$9 == 500 {print $7}' access.log

Extract URLs with 500 errors

awk -F, '{print $2, $3}' data.csv

Process a CSV file

awk 'BEGIN{OFS=\",\"} {print $1, $2}' file

Output as CSV

awk '{sum+=$5} END{print sum/1024/1024 \" MB\"}' file

Sum a column and convert units

Tips

awk splits on whitespace or tabs by default; use -F to specify another separator.
The BEGIN block runs before processing, the END block runs after.
awk arrays are associative (hash tables); keys can be strings.

Official References

Each command links to its official documentation below, so you can verify the latest usage and read deeper.

Linux man-pages

Maintained by LaoHand

Publicly updated on Jul 21, 2026, continuously proofread against official docs.

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