Basics

Basic Usage

`awk '{print}' file.txt`	Print all lines
`awk '{print $1}' file.txt`	Print first field
`awk '{print $NF}' file.txt`	Print last field
`awk -F: '{print $1}' /etc/passwd`	Use : as delimiter
`awk 'NR==5' file.txt`	Print line 5

Variables

Built-in variables

$0  # Entire line
$1  # First field
$NF # Last field
NF  # Number of fields
NR  # Line number
FS  # Field separator
OFS # Output field separator

Patterns

Pattern Matching

Conditions

awk '/error/' file.txt           # Match pattern
awk '$1 == "John"' file.txt      # Field equals
awk '$3 > 100' file.txt          # Numeric comparison
awk '$2 ~ /pattern/' file.txt    # Regex match

Examples

Common Tasks

Useful examples

# Sum a column
awk '{sum += $1} END {print sum}' file.txt

# Count occurrences
awk '{count[$1]++} END {for (k in count) print k, count[k]}' file.txt

# Remove duplicates
awk '!seen[$0]++' file.txt

# Calculate average
awk '{sum+=$1; n++} END {print sum/n}' file.txt