debian-bash/lib/functions.sh

# idempotent apt install [package1 package2 ...]
function idem_apt_install() {
  for i in $@; do
    if ! (/usr/bin/dpkg-query --status "$i" >/dev/null 2>&1); then
      sudo apt install -y "$i"
    else
      $VERBOSE && echo "${PREFIX:=}apt package <$i> already installed!"
    fi
  done
}

##
# return 0 (true) if array (passed by name) contains element
# usage:
#   ARRAY = ( a b c )
#   containsElement ARRAY 'a' => 0
containsElement() {
  local -a 'arraykeys=("${!'"$1"'[@]}")'
  if $(isArray $1); then
    for index in ${arraykeys[*]}; do
      current=$1"[$index]"
      [[ "${!current}" == "$2" ]] && return 0 # found
    done
    return 1 # not found
  else
    echo >&2 "ERROR: $1 not an array!"
    return 2 # not an array
  fi
}

isArray() {
  [[ "$(declare -p $1 2>/dev/null)" =~ "declare -a" ]] && return 0 # is an array
  return 1                                                         # not an array
}

##
#
askConfirmation() {
  case "$1" in
  y | Y | yes | YES)
    QUESTION="(Y/n)?"
    DEFAULT=0
    ;;
  *)
    QUESTION="(y/N)?"
    DEFAULT=1
    ;;
  esac
  read -p "$QUESTION : " choice
  case "$choice" in
  y | Y | yes | YES) return 0 ;; #true
  n | no | N | NO) return 1 ;;   #false
  *) return $DEFAULT ;;
  esac
}