Installs or upgrades kubectl on Linux, including WSL2

install_upgrade_kubectl.sh

#!/usr/bin/env bash
# Installs or upgrades kubectl on Linux

# Chuck for root privileges
if [[ "$EUID" != "0" ]] ; then
  echo "Please execute script with sudo or as root."
  exit 1
fi

# Check Dependencies
if ! curl --version &>/dev/null; then
  echo "curl must be installed and in \$PATH"
  exit 1
fi

INSTALLED_KUBECTL_PATH=$(which kubectl 2>/dev/null || echo NONE)
INSTALLED_KUBECTL_VERSION="$($INSTALLED_KUBECTL version --client --short | cut -f3 -d' ')"

LATEST_KUBECTL_VERSION=$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)

if [ $INSTALLED_KUBECTL_VERSION != $LATEST_KUBECTL_VERSION ] ; then
  curl -#LO "https://storage.googleapis.com/kubernetes-release/release/${LATEST_KUBECTL_VERSION}/bin/linux/amd64/kubectl" \
    && chmod ug+x ./kubectl
  if [ -x ./kubectl ] ; then
    DOWNLOADED_KUBECTL_VERSION="$(./kubectl version --client --short | cut -f3 -d' ')"
  fi
else
  echo "The latest version is already installed."
fi

if [ $DOWNLOADED_KUBECTL_VERSION != $LATEST_KUBECTL_VERSION ] ; then
  echo "ERROR: Something went wrong with the download."
else
  mv ./kubectl $INSTALLED_KUBECTL_PATH
  echo "Installation and/or upgrade complete."
fi

# EOF