container-image-name

go.mod

module github.com/flavio/container-image-name

go 1.16

require (
	github.com/docker/distribution v2.7.1+incompatible
	github.com/opencontainers/go-digest v1.0.0 // indirect
)

go.sum

github.com/docker/distribution v2.7.1+incompatible h1:a5mlkVzth6W5A4fOsS3D2EO5BUmsJpcB+cRlLU7cSug=
github.com/docker/distribution v2.7.1+incompatible/go.mod h1:J2gT2udsDAN96Uj4KfcMRqY0/ypR+oyYUYmja8H+y+w=
github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8Oi/yOhh5U=
github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=

main.go

package main

import (
	_ "crypto/sha256"
	_ "crypto/sha512"
	"fmt"
	"github.com/docker/distribution/reference"
	"os"
)

type Image struct {
	Registry   string
	Repository string
	Tag        string
	Digest     string
}

func main() {
	if len(os.Args) != 2 {
		fmt.Println("Wrong number of args")
		os.Exit(1)
	}

	refStr := os.Args[1]
	named, err := reference.ParseNormalizedNamed(refStr)
	if err != nil {
		fmt.Printf("Cannot parse image name: %+v\n", err)
		os.Exit(1)
	}

	// Add the latest lag if they did not provide one.
	named = reference.TagNameOnly(named)

	i := Image{
		Registry:   reference.Domain(named),
		Repository: reference.Path(named),
	}

	// Add the tag if there was one.
	if tagged, ok := named.(reference.Tagged); ok {
		i.Tag = tagged.Tag()
	} else {
		i.Tag = "-"
	}

	// Add the digest if there was one.
	if canonical, ok := named.(reference.Canonical); ok {
		digest := canonical.Digest()
		i.Digest = string(digest)
	} else {
		i.Digest = "-"
	}

	fmt.Printf("%s - %+v", named, i)
}

test.sh

#!/bin/bash

INPUT_NAMES=(
  "busybox"
  "test.com:tag"
  "test.com:5000"
  "test.com/repo:tag"
  "test:5000/repo:tag"
  "test:5000/repo@sha256:ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
  "test:5000/repo:tag@sha256:ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
  "lowercase:Uppercase"
  "sub-dom1.foo.com/bar/baz/quux"
  "sub-dom1.foo.com/bar/baz/quux:some-long-tag"
  "b.gcr.io/test.example.com/my-app:test.example.com"
  "xn--n3h.com/myimage:xn--n3h.com"
  "xn--7o8h.com/myimage:xn--7o8h.com@sha512:ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
  "foo_bar.com:8080"
  "foo/foo_bar.com:8080"
)

for image in "${INPUT_NAMES[@]}"
do
  echo "$image -> $(./container-image-name ${image})"
done

A simple way to see how container image names are actually parsed by Docker.

Building

• Create a directory called container-image-name
• go build

Usage

Just run:

./test.sh