which(1) implemented in Go

which.go

package main

import (
	"flag"
	"os"
	"path"
	"strings"
)

func main() {
	flag.Parse()
	var progToFind string
	if len(flag.Args()) >= 1 {
		progToFind = flag.Args()[0]
	}
	if envpaths := os.Getenv("PATH"); len(envpaths) > 0 {
		dirs := strings.Split(envpaths, ":")
		for _, dir := range dirs {
			testPath := path.Join(dir, progToFind)
			_, err := os.Stat(testPath)
			if err == nil {
				println(testPath)
				return
			}
			if os.IsNotExist(err) {
				continue
			}
		}
	}
	return
}