get-k8s.sh

#!/bin/sh

# posix complaint
# verified by https://www.shellcheck.net

#
# usage: get-k8s.sh FLAGS [stable|latest|ci|<version>] [client|node|server|src|test|<file>]
#
# FLAGS
#    -s    Enable streaming. Instead of inflating the K8s tarball, the
#          script redirects the curl process into stdout, making it possible
#          to pipe this script into a custom tar command.
#

# Parse the flags.
while getopts "s" opt; do
  case "${opt}" in
    s)
      streaming=true
      shift
      ;;
    *)
      ;;
  esac
done

# Determine the version to fetch.
K8S_VERSION=${1:-${K8S_VERSION}}
if [ -z "${K8S_VERSION}" ]; then K8S_VERSION=release/stable.txt; fi
case ${K8S_VERSION} in
stable)
  K8S_VERSION=release/stable.txt
  ;;
latest)
  K8S_VERSION=release/latest.txt
  ;;
ci)
  K8S_VERSION=ci/latest.txt
  ;;
esac

# Determine which bits to fetch.
K8S_TYPE=${2:-${K8S_TYPE}}
if [ -z "${K8S_TYPE}" ]; then K8S_TYPE=server; fi
case ${K8S_TYPE} in
client)
  K8S_TGZ=kubernetes-client-linux-amd64.tar.gz
  ;;
node)
  K8S_TGZ=kubernetes-node-linux-amd64.tar.gz
  ;;
server)
  K8S_TGZ=kubernetes-server-linux-amd64.tar.gz
  ;;
src)
  K8S_TGZ=kubernetes-src.tar.gz
  ;;
test)
  K8S_TGZ=kubernetes-test.tar.gz
  ;;
*)
  K8S_TGZ=${K8S_TYPE}
  ;;
esac

# This is the base URL for getting the K8s bits.
K8S_URL=https://storage.googleapis.com/kubernetes-release

# If the version does *not* begin with release/ then it's a dev version
if ! echo "${K8S_VERSION}" | grep '^release/' >/dev/null 2>&1; then
  K8S_URL=${K8S_URL}-dev
fi

# If the version points to a .txt file then its *that* file that contains
# the actual version information.
if echo "${K8S_VERSION}" | grep '\.txt$' >/dev/null 2>&1; then
  K8S_REAL_VERSION=$(curl --retry-max-time 120 -sL ${K8S_URL}/${K8S_VERSION})
  K8S_VERSION_PREFIX=$(echo "${K8S_VERSION}" | awk -F/ '{print $1}')
  K8S_VERSION=${K8S_VERSION_PREFIX}/${K8S_REAL_VERSION}
fi

# Build the actual artifact URL.
K8S_ARTIFACT=${K8S_URL}/${K8S_VERSION}/${K8S_TGZ}

# Get the bits and inflate them to the current directory.
printf 'VERSION\t%s\nURL\t%s\n' "${K8S_VERSION}" "${K8S_ARTIFACT}" >/dev/stderr

# Create a temp file to store information about the artifact.
temp_file=$(mktemp)
curl -sSIL "${K8S_ARTIFACT}" > "${temp_file}"

# If the response wasn't 200 then the artifact does not exist.
if [ -z "$(grep '^HTTP.\{0,\}200[[:space:]]\{0,\}$' "${temp_file}" | \
        tail -n1)" ]; then
  printf '\nThe artifact at the specified URL does not exist\n' >/dev/stderr
  exit 1
fi

# Print the size of the artifact that will be downloaded.
bytes="$(grep -i '^content-length:' "${temp_file}" | \
         tail -n1 | awk '{print $2}' | tr -d '\r')"
if [ -n "${bytes}" ]; then
  # bytes
  if [ "${bytes}" -lt "1024" ]; then
    printf 'SIZE\t%sb\n' "${bytes}" >/dev/stderr
  # kilobytes
  elif [ "${bytes}" -lt "1048576" ]; then
    printf 'SIZE\t%sKiB\n' "$((bytes/1024))" >/dev/stderr
  # megabytes
  elif [ "${bytes}" -lt "1073741824" ]; then
    printf 'SIZE\t%sMiB\n' "$((bytes/1024/1024))" >/dev/stderr
  # gigabytes
  else
    printf 'SIZE\t%dkGiB\n' "$((bytes/1024/1024))" >/dev/stderr
  fi
  echo >/dev/stderr
fi

# Remove the temp file.
rm -f "${temp_file}"

# Fetch the tarball and inflate it into the current directory.
if [ "${streaming}" = "true" ]; then
  curl --retry-max-time 120 -L "${K8S_ARTIFACT}"
else
  curl --retry-max-time 120 -L "${K8S_ARTIFACT}" | tar -xz
fi