Select kubectl binary by version

kubectl-use_version

#!/bin/bash

function download()
{
  KUBECTL_VERSIONS=(
    $(curl -s "https://api.github.com/repos/kubernetes/kubernetes/releases?per_page=100" \
      | jq -r '.[] | .tag_name' \
      | grep '^v[0-9]\.[0-9][0-9]\?\.[0-9][0-9]\?$' \
      | sort -Vr \
      | awk -F . '!a[$1 FS $2]++' \
      | sort -V)
  )

  echo Found ${#KUBECTL_VERSIONS[*]} kubectl versions: ${KUBECTL_VERSIONS[*]}

  for version in ${KUBECTL_VERSIONS[@]}; do
    bin=kubectl_${version}

    if [ -e "$bin" ]; then
      echo Already exists: $bin
    else
      echo Downloading $bin
      curl -skL https://storage.googleapis.com/kubernetes-release/release/${version}/bin/linux/amd64/kubectl > $bin
    fi
  done
}

function usage()
{
  echo 'Usage: kubectl use-version [--download]'
  echo
  echo 'This command creates a symlink `kubectl` -> `kubectl_v[VERSION]` for the selected version available in your system.'
  echo
  echo 'You can download latest kubectl versions using the flag `--download`:'
  echo
  echo '$ mkdir ~/bin'
  echo '$ cd ~/bin'
  echo '$ kubectl use-version --download'
  echo '$ export PATH="$PATH:~/bin"'
  echo '$ kubectl use-version'

  exit ${1:-0}
}

while [ $# -gt  0 ]; do
  case $1 in
    -h|--help) usage ;;
    -d|--download) download; exit
  esac
done

if ! KUBECTL_BIN=$(which kubectl 2>/dev/null); then
  echo kubectl not found in PATH
  exit 1
fi

if ! [ -L "$KUBECTL_BIN" ]; then
  echo kubectl is not a symlink
  exit 1
fi

KUBECTL_DIR=${KUBECTL_BIN%/*}

shopt -s nullglob
KUBECTL_VERSIONS=(
  ${KUBECTL_DIR}/kubectl_v*
)
shopt -u nullglob

if [ ${#KUBECTL_VERSIONS[*]} -eq 0 ]; then
  echo "No kubectl binaries found in $KUBECTL_DIR: expected filename format is 'kubectl_v[VERSION]'"
  exit 1
fi

KUBECTL_TARGET=$(printf "%s\n" ${KUBECTL_VERSIONS[*]} | sort -n -r | fzf -1 --ansi --no-preview --cycle)

if [ -f "$KUBECTL_TARGET" ]; then
  ln -vfs "$KUBECTL_TARGET" "$KUBECTL_BIN"
fi