bash-docker-is-disk-space-usage-above-limit

is_docker_disk_space_usage_above_limit.sh

#!/bin/bash
# --
# Test if Docker daemon disk space usage is above a given limit in bytes.
#
# Example 1: Docker disk space usage is above limit 
#
#    $ source is_docker_disk_space_usage_above_limit.sh
#    $ is_docker_disk_space_usage_above_limit 1
#    Docker disk space usage is above limit (actual: 1050000005B, limit: 1B)
#    $ printf $?
#    0
#
# Example 2: Docker disk space usage is below or equal to limit
#
#    $ source is_docker_disk_space_usage_above_limit.sh
#    $ is_docker_disk_space_usage_above_limit 1000000000000
#    Docker disk space usage is below or equal to limit (actual: 1050000005B, limit: 1000000000000B)
#    $ printf $?
#    1
# 
# --
iec_string_to_bytes() {
  local iec_string=$1
      iec_format_pattern='([0-9.]+)\s*([kMGTP]?B)'

  if ! [[ "${iec_string}" =~ ${iec_format_pattern} ]]; then
    printf "Input string has invalid format (received: \"%s\", expected: \"%s\")." "$1" "${iec_format_pattern}"
    return 1
  fi 
    
  local number_value="${BASH_REMATCH[1]}"
    iec_unit="${BASH_REMATCH[2]}"
    factor=""

  case "${iec_unit}" in 
    B) factor=1;;
    kB) factor=1000;;
    MB) factor=1000000;;
    GB) factor=1000000000;;
    TB) factor=1000000000000;;
    PB) factor=1000000000000000;;
  esac

  # We use scale=0 here to drop the (redundant) decimal points.
  # This only works with division so we divide by one.
  printf "scale=0;%s * %s/1\n" "${number_value}" "${factor}" \
    | bc 
}

calculate_docker_total_disk_space_usage() {
  local bc_expression="0"
    disk_space_used="$(docker system df --format='{{.Size}}' | tr '\n' ' ')"

  for disk_space_used_by_resource in ${disk_space_used}; do 
    # shellcheck disable=SC2086
    disk_space_used_by_resource_bytes="$(iec_string_to_bytes \"${disk_space_used_by_resource}\")"
    bc_expression="${bc_expression} + ${disk_space_used_by_resource_bytes}"
  done 

  printf "%s\n" "${bc_expression}" \
    | bc
}

is_docker_disk_space_usage_above_limit() {
  local disk_space_limit=$1
    docker_disk_space_used="$(calculate_docker_total_disk_space_usage)"
    docker_disk_space_usage_is_above_limit="$(printf '%s > %s\n' ${docker_disk_space_used} ${disk_space_limit} | bc -l)"

  # Note that bc returns 1 if the comparison is true and 0 otherwise.
  if [ "${docker_disk_space_usage_is_above_limit}" -eq 1 ]; then 
    printf "Docker disk space usage is above limit (actual: %sB, limit: %sB)" "${docker_disk_space_used}" "${disk_space_limit}"
    return 0
  fi 

  printf "Docker disk space usage is below or equal to limit (actual: %sB, limit: %sB)" "${docker_disk_space_used}" "${disk_space_limit}"
  return 1
}