Overview

AWK is a text processing language for scanning files, selecting lines that match patterns, and performing actions on those lines.

Basic syntax

• Pattern and action: awk 'pattern { action }' file
• Pipeline input: command | awk 'pattern { action }'
• If no pattern is provided, the action applies to all lines
• If no action is provided, matching lines are printed by default

Fields

• Set input field separator: -F option or FS variable
• $1 first field
• $5 fifth field
• $0 entire input line

Built-in functions

• print arg1 arg2 — print arguments to stdout
• print arg1, arg2 — print with separator (OFS, default space)
• printf "format", arg1, arg2 — print with formatting
• gsub(/ere/, replace, input) — global substitution in input; returns substitution count
• tolower(str) — convert to lowercase
• toupper(str) — convert to uppercase
• substr(str, start, len) — substring