Jamf Pro extension attribute for creating arbitrary groups of arbitrary size

staggered_rollout_number

#!/bin/bash

####################################################################
#                              \\\///                              #
#                             / _  _ \                             #
#                           (| (.)(.) |)                           #
# .-----------------------.OOOo--()--oOOO.-----------------------. #
# |                                                              | #
# | Test whether the machine has assigned itself a random number | #
# | for rolling out policies in staggered groups and assign one  | #
# | if not                                                       | #
# |                                                              | #
# | Version 1.0                                                  | #
# |                                                              | #
# '-----------------------.oooO----------------------------------' #
#                          (   )   Oooo.                           #
#                           \ (    (   )                           #
#                            \_)    ) /                            #
#                                  (_/                             #
#                                                                  #
# https://boxes.thomasjensen.com/                                  #
####################################################################

export PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin

readonly RANGE_BOTTOM=1
readonly RANGE_TOP=8176
readonly DATA_FILE="/Library/Application Support/JamfAdmin/clientData.plist"

hash -p /usr/libexec/PlistBuddy PlistBuddy

function get_staggered_rollout_number() {
  local silent="false"
  while getopts "s" flag; do
    case "${flag}" in
    s)
      silent="true"
      ;;
    *) ;;
    esac
  done
  result="$(
    PlistBuddy -c \
      "print :StaggeredRolloutNumber" \
      "${DATA_FILE}" \
      2>/dev/null
  )"
  # test whether result is a nonzero positive integer - in testing, some
  # clients had blank values and PListBuddy writes them as zeroes when the type
  # is 'integer'
  if [[ "${result}" -eq "${result}" && "${result}" -ge 1 ]] 2>/dev/null; then
    # added -s flag to be able to use this function for control flow
    if [[ "${silent}" == "false" ]]; then
      echo "${result}"
    fi
    return 0
  fi
  return 1
}

function add_staggered_rollout_number() {
  local entry="StaggeredRolloutNumber"
  local type="integer"
  local value
  read -r value
  PlistBuddy -c \
    "add :${entry} ${type} ${value}" \
    "${DATA_FILE}" \
    &>/dev/null
}

function set_staggered_rollout_number() {
  local entry="StaggeredRolloutNumber"
  local value
  read -r value
  PlistBuddy -c \
    "set :${entry} ${value}" \
    "${DATA_FILE}" \
    &>/dev/null
}

function generate_random_number_within_range() {
  awk \
    -v RANGE_TOP="${RANGE_TOP}" \
    -v RANGE_BOTTOM="${RANGE_BOTTOM}" \
    'BEGIN {
      srand()
      print  int(b + rand() * (RANGE_TOP - RANGE_BOTTOM + 1))
    }'
  # not sure if this is what produced the zeros mentioned in the
  # get_staggered_rollout_number comment but it looks to be working more
  # consistently with this pause
  sleep .25
}

function print_enclosed_in_result_tags() {
  read -r result
  echo "<result>${result}</result>"
}

function main() {
  mkdir -p "$(dirname "${DATA_FILE}")"
  while ! get_staggered_rollout_number -s; do
    num=$(generate_random_number_within_range)
    add_staggered_rollout_number <<<"${num}" ||
      set_staggered_rollout_number <<<"${num}"
  done
  get_staggered_rollout_number |
    print_enclosed_in_result_tags
}

main