A line counting utility in golang

linecount.go

package main

import (
	"bytes"
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
)

func main() {
	flag.Parse()
	patternStrings := flag.Args()

	filenMatchCounts := make([]int, len(patternStrings))
	lineCounts := make([]int, len(patternStrings))

	defer func() {
		totalLineseCount := 0
		totalFilesMatched := 0

		for i, patternString := range patternStrings {
			totalLineseCount += lineCounts[i]
			totalFilesMatched += filenMatchCounts[i]

			fmt.Printf("%8d\t%8d\t%s\n", filenMatchCounts[i], lineCounts[i], patternString)
		}
		fmt.Printf("\n%8d\t%8d\n", totalFilesMatched, totalLineseCount)
	}()

	wd, _ := os.Getwd()
	walkErr := filepath.Walk(wd, func(path string, info os.FileInfo, err error) error {
		// fmt.Printf("\n%8d\t%10d\t%s\n", totalFilesMatched, totalLineseCount, path)
		if !info.IsDir() {
			for i, pattern := range patternStrings {
				if matches, err := filepath.Match(pattern, info.Name()); matches && err == nil {
					filenMatchCounts[i]++
					file, openErr := os.Open(path)
					defer file.Close()
					if openErr != nil {
						log.Printf("[ERROR] %s", openErr)
						return nil
					}
					count, countErr := lineCounter(file)
					if countErr != nil {
						log.Printf("[ERROR] %s", countErr)
						return nil
					}
					lineCounts[i] += count
				} else if matches && err != nil {
					log.Printf("[ERROR] %s", err)
					return nil
				}
			}
		}
		return nil
	})

	if walkErr != nil {
		fmt.Println("Error: " + walkErr.Error())
	}
}

func lineCounter(r io.Reader) (int, error) {
	buf := make([]byte, 32*1024)
	count := 0
	lineSep := []byte{'\n'}

	for {
		c, err := r.Read(buf)
		count += bytes.Count(buf[:c], lineSep)

		switch {
		case err == io.EOF:
			return count, nil

		case err != nil:
			return count, err
		}
	}
}