uawk

AWK interpreter written in Go with coregex regex engine.

Features

• POSIX AWK compliant with GNU AWK extensions
• Parallel file processing (-j N)
• Embeddable Go API
• Zero CGO dependencies

Installation

go install github.com/kolkov/uawk/cmd/uawk@latest

Usage

Command Line

# Basic usage
uawk '{ print $1 }' file.txt

# Field separator
uawk -F: '{ print $1 }' /etc/passwd

# Variables
uawk -v name=World 'BEGIN { print "Hello, " name }'

# Program from file
uawk -f script.awk input.txt

# Parallel processing
uawk -j 4 '{ sum += $1 } END { print sum }' *.log

# Non-POSIX regex mode
uawk --no-posix '/pattern/ { print }' file.txt

As a Library

package main

import (
    "fmt"
    "strings"
    "github.com/kolkov/uawk"
)

func main() {
    output, err := uawk.Run(`{ print $1 }`, strings.NewReader("hello world"), nil)
    if err != nil {
        panic(err)
    }
    fmt.Print(output)

    // With configuration
    config := &uawk.Config{
        FS: ":",
        Variables: map[string]string{"threshold": "100"},
    }
    output, err = uawk.Run(`$2 > threshold { print $1 }`, input, config)

    // Compile once, run multiple times
    prog, err := uawk.Compile(`{ sum += $1 } END { print sum }`)
    for _, file := range files {
        result, _ := prog.Run(file, nil)
        fmt.Println(result)
    }
}

Benchmarks

See uawk-bench for benchmark suite and methodology.

Results vary by workload. Regex-heavy patterns benefit from coregex optimizations. I/O-bound workloads show smaller differences between implementations.

Building

git clone https://github.com/kolkov/uawk
cd uawk
go build -o uawk ./cmd/uawk

Requires Go 1.25+.

Architecture

Source → Lexer → Parser → AST → Semantic Analysis → Compiler → Optimizer → VM

Component	Description
Lexer	Context-sensitive tokenizer, UTF-8
Parser	Recursive descent
Compiler	Bytecode generation (~110 opcodes)
Optimizer	Peephole optimization
VM	Stack-based execution

Supported Features

Standard AWK

• Pattern-action rules, BEGIN/END blocks
• Field splitting and assignment
• Built-in variables (NR, NF, FS, RS, OFS, ORS, FILENAME, etc.)
• Arithmetic, string, and regex operators
• Control flow (if/else, while, for, do-while)
• Associative arrays
• Built-in functions (print, printf, sprintf, length, substr, split, sub, gsub, match, tolower, toupper, sin, cos, exp, log, sqrt, int, rand, srand, system, etc.)
• User-defined functions
• I/O redirection (>, >>, |, getline)

Extensions

• -j N parallel execution
• -c Unicode character operations
• --posix / --no-posix regex mode
• Debug flags (-d, -da, -dt)

License

MIT

Acknowledgments

• GoAWK by Ben Hoyt — reference implementation and test suite
• coregex — regex engine