gistfile1.go

package main

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

type Template struct {
   content string
   length  int
}

var template Template

func add_header(path, content string) {
   file, _ := os.OpenFile(path, os.O_RDWR, 0777)
   file.WriteAt([]byte(template.content+content), 0)
   file.Close()
}

func walk_directory(path string, f os.FileInfo, err error) error {
   if !strings.HasSuffix(path, ".go") {
      return nil
   }

   obytes, _ := ioutil.ReadFile(path)
   output := string(obytes)

   if template.length > len(output) {
      add_header(path, output)
      fmt.Printf("Modified file %s.", path)
      return nil
   }

   if output[0:template.length] != template.content {
      return nil
   }

   return nil
}

func mkpath(entity string) string {
   wd, _ := os.Getwd()
   return strings.Join([]string{wd, entity}, string(os.PathSeparator))
}

func main() {
   btemp, _ := ioutil.ReadFile(mkpath(".template.go"))
   template = Template{content: string(btemp), length: len(string(btemp))}

   flag.Parse()
   if flag.Arg(0) == "" {
      return
   } else {
      err := filepath.Walk(mkpath(flag.Arg(0)), walk_directory)
      if err != nil {
         fmt.Printf("filepath.Walk() returned %v\n", err)
      }
   }
}