Write chef node names and public ip addresses to /etc/hosts

chef_hostsfile.sh

#!/bin/bash

set -euo pipefail

HEADER='# All lines below managed by chef_hostfile.sh'

backup_hostsfile() {
  sudo cp /etc/hosts{,.$(date +%s)}
}

write_hostsfile() {
  [[ -z "$1" ]] && [[ ! -e "$1" ]] && echo "ERROR! Calling write_hostsfile() with invalid filename: $1"
  if ! git diff /etc/hosts "$1"; then
    read -p 'Overwrite /etc/hosts with this change? (y/N)' -n 1 -r
    echo
    if [[ $REPLY =~ ^[Yy]$ ]]; then
      cat "$1" | sudo tee /etc/hosts > /dev/null
    fi
  fi
}

main() {
  backup_hostsfile

  local tmpfile=$(mktemp "${TMPDIR:-/tmp/}$(basename $0).XXXXXXXXXXXX")

  # strip everything after and including $HEADER into a new file
  sed '/^'"${HEADER}"'/,$ d' /etc/hosts | tee "$tmpfile"
  echo "$HEADER" | tee -a "$tmpfile"

  while IFS=" " read -r ip name; do
    echo "$(printf "%-16s%s\n" "$ip" "$name")" | tee -a "$tmpfile"
  done <<< "$(knife search node 'cloud_public_ipv4:*' -a cloud.public_ipv4 -Fjson \
    | jq -r '.rows[]|to_entries|map("\(.value|."cloud.public_ipv4") \(.key)")|.[]' \
    | sort -k 2 )"

  write_hostsfile "$tmpfile"

  rm "$tmpfile"
}

main "$@"