Multigrep - Multithreaded grep in go

multigrep.go

package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strings"
	"sync"
)

var (
	searchString string
	rootFolder   string
	numThreads   int
	wg           sync.WaitGroup
	matches      []string
)

func main() {
	// Parse command line arguments
	flag.StringVar(&searchString, "s", "", "String to search for")
	flag.StringVar(&rootFolder, "f", "", "Root folder to search in")
	flag.IntVar(&numThreads, "t", 10, "Number of threads")
	flag.Parse()

	if searchString == "" || rootFolder == "" {
		log.Fatal("String to search (-s) and root folder (-f) must be provided")
	}

	err := filepath.Walk(rootFolder, processFile)
	if err != nil {
		log.Fatal(err)
	}

	wg.Wait()

	if len(matches) == 0 {
		fmt.Println("No matches found.")
	} else {
		for _, match := range matches {
			fmt.Println(match)
		}
	}
}

func processFile(path string, info os.FileInfo, err error) error {
	if err != nil {
		log.Println(err)
		return nil
	}

	if info.IsDir() {
		return nil
	}

	wg.Add(1)

	go func() {
		defer wg.Done()

		content, err := ioutil.ReadFile(path)
		if err != nil {
			log.Println(err)
			return
		}

		lines := strings.Split(string(content), "\n")

		for _, line := range lines {
			if strings.Contains(line, searchString) {
				matches = append(matches, line)
			}
		}
	}()

	return nil
}