A simple grep implementation in Go

grep.go

package main

import(
  "bufio"
  "fmt"
  "log"
  "os"
  "regexp"
)

func handleLine(line string) {
  matched, err := regexp.MatchString(os.Args[1], line)

  if err != nil {
    log.Fatal(err)
  } else if matched {
    fmt.Println(line)
  }
}

func main() {
  scanner := bufio.NewScanner(os.Stdin)

  for scanner.Scan() {
    handleLine(scanner.Text())
  }

  if err := scanner.Err(); err != nil {
    log.Fatal(err)
  }
}

oof, this is pretty painful, you match and check for err on every Scan(), what you should do is

r, err := regexp.Compile(os.Args[1])

and then every Scan()

if r.MatchString(scanner.Text()) {fmt.Println(scanner.Text())}

no need for handleLine() function at all