Check whether an image exists Dockerhub.

Docker-Tag-Exists.PS1

# Check whether a docker image exists on Dockerhub. 
#
# Usage:
#   if (Docker-Tag-Exists -Repository "unityci/base" -Tag "windows-0.17.0") {
#     echo "Image exists."
#   } else {
#     echo "Image does not exist."
#   }
function Docker-Tag-Exists {
  [CmdletBinding()]
  param([string] $Repository, [string] $Tag)

  Try {
    Invoke-RestMethod "https://index.docker.io/v1/repositories/$Repository/tags/$Tag"
  } Catch {} # Assume image does not exist on erroneous response

  return $?
}

dockerTagExists.sh

#!/bin/sh

# Check whether a docker image exists on Dockerhub. 
#
# Source: https://stackoverflow.com/a/39731444/3593896
#
# Usage:
#   if docker_tag_exists "unityci/base" "ubuntu-0.17.0" ; then
#     echo "Image exists."
#   else
#     echo "Image does not exists."
#   fi
function docker_tag_exists() {
  curl --silent -f -lSL https://index.docker.io/v1/repositories/$1/tags/$2 > /dev/null
}