Golang : Convert octal value to string to deal with leading zero problem

Problem :

You have some integer variables or input data that starts with zero and they are causing some funky bugs when displayed on screen in your program. This is known as the leading zero problem and plagued other programming languages as well. Not unique to Golang alone and the developers behind Golang won't fix this issue.

So how to fix this leading zero problem ?

Solution :

At this moment, reflect package still unable to detect if an integer variable is octal or strings.HasPrefix() can be used to check the integer starts with zero.( only works on string).

Therefore, to be safe, always convert the integer variables to string before displaying the values.

 package main

 import (

 func main() {
  var octalInt = 0012

  // don't use this method as the leading zero will disappear!
  zip := strconv.FormatInt(int64(octalInt), 8) // base 8 for Octal
  fmt.Println("Wrong! Don't use this method because of : ")
  fmt.Println("Missing zero : ", zip)
  fmt.Printf("Type : %v \n", reflect.TypeOf(zip))


  // calculate the size of the octal - the wrong way!
  t := reflect.TypeOf(octalInt)
  fmt.Println("Type : ", t)

  // play.golang.org will return 4
  // go run will return 8 ... so not to be trusted for now
  fmt.Println("Size : ", t.Size())

  fmt.Println("However, we have to count by hand on the actual size of the octalInt")

  str := fmt.Sprintf("00%o", octalInt) //pad zero up to the length of 4, o is for expecting octal value

  // ** NOTE : Have to hardcode 4 because there is no way I can programmatically insert octalInt's length into
  // fmt.Sprintf()

  fmt.Println("Converted from integer(octal) to string : ", str)
  fmt.Printf("Type : %v \n", reflect.TypeOf(str))

Output :

Wrong! Don't use this method because of :

Missing zero : 12

Type : string


Type : int

Size : 8

However, we have to count by hand on the actual size of the octalInt

Converted from integer(octal) to string : 0012

Type : string

  See also : Golang : Dealing with postal or zip code example

By Adam Ng

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