Parse BASH script input arguments in a simplest way

_commons.sh

#!/usr/bin/env bash
# shellcheck disable=SC2155,SC2034,SC2059

# get script directory
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

# is allowed to use macOS extensions (script can be executed in *nix environment)
use_macos_extensions=false
if [[ "$OSTYPE" == "darwin"* ]]; then use_macos_extensions=true; fi

# colors
export cl_reset=$(tput sgr0)

export cl_red=$(tput setaf 1)
export cl_green=$(tput setaf 2)
export cl_yellow=$(tput setaf 3)
export cl_blue=$(tput setaf 4)
export cl_purple=$(tput setaf 5)
export cl_cyan=$(tput setaf 6)
export cl_white=$(tput setaf 7)
export cl_grey=$(tput setaf 8)

export cl_lred=$(tput setaf 9)
export cl_lgreen=$(tput setaf 10)
export cl_lyellow=$(tput setaf 11)
export cl_lblue=$(tput setaf 12)
export cl_lpurple=$(tput setaf 13)
export cl_lcyan=$(tput setaf 14)
export cl_lwhite=$(tput setaf 15)
export cl_black=$(tput setaf 16)

# shellcheck disable=SC1090 source=_logger.sh
source "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/_logger.sh"
# register own logger
logger common "$@"

function now() {
  echo "$EPOCHREALTIME" # <~ bash 5.0
  #python -c 'import datetime; print datetime.datetime.now().strftime("%s.%f")'
}

# shellcheck disable=SC2155,SC2086
function print_time_diff() {
  local diff="$(now) - $1"
  bc <<<$diff
}

# shellcheck disable=SC2086
function validate_input() {
  local variable=$1
  local default=${2:-""}
  local prompt=${3:-""}
  local user_in=""

  # Ctrl+C during read operation force error exit
  trap 'exit 1' SIGINT

  # execute at least once
  while :; do
    # allow macOs read command extension usage (default value -i)
    if $use_macos_extensions; then
      [[ -z "${prompt// /}" ]] || read -e -i "${default}" -p "${cl_purple}? ${cl_reset}${prompt}${cl_blue}" -r user_in
      [[ -n "${prompt// /}" ]] || read -e -i "${default}" -r user_in
    else
      [[ -z "${prompt// /}" ]] || echo "${cl_purple}? ${cl_reset}${prompt}${cl_blue}"
      read -r user_in
    fi
    printf "${cl_reset}"
    [[ -z "${user_in// /}" ]] || break
  done

  local __resultvar=$variable
  eval $__resultvar="'$user_in'"
}

# shellcheck disable=SC2086,SC2059
function validate_yn_input() {
  local variable=$1
  local default=${2:-""}
  local prompt=${3:-""}
  local user_in=false

  while true; do
    if $use_macos_extensions; then
      [[ -z "${prompt// /}" ]] || read -e -i "${default}" -p "${cl_purple}? ${cl_reset}${prompt}${cl_blue}" -r yn
      [[ -n "${prompt// /}" ]] || read -e -i "${default}" -r yn
    else
      [[ -z "${prompt// /}" ]] || echo "${cl_purple}? ${cl_reset}${prompt}${cl_blue}"
      read -r yn
    fi
    printf "${cl_reset}"
    case $yn in
    [Yy]*)
      user_in=true
      break
      ;;
    [Nn]*)
      user_in=false
      break
      ;;
    *)
      user_in=false
      break
      ;;
    esac
  done
  local __resultvar=$variable
  eval $__resultvar="$user_in"
}

# shellcheck disable=SC2086
function env_variable_or_secret_file() {
  #
  # Usage:
  #     env_variable_or_secret_file "new_value" \
  #       "GITLAB_CI_INTEGRATION_TEST" \
  #       ".secrets/gitlab_ci_integration_test" \
  #       "{user friendly message}"
  #
  local name=$1
  local variable=$2
  local file=$3
  local fallback=${4:-"No hints, check the documentation"}
  local __result=$name

  if [[ -z "${!variable}" ]]; then
    if [[ ! -f "$file" ]]; then
      echo ""
      echo "${cl_red}ERROR:${cl_reset} shell environment variable '\$$variable' or file '$file' should be provided"
      echo ""
      echo "Hint:"
      echo "  $fallback"
      exit 1
    else
      echo "Using file: ${cl_green}$file${cl_reset} ~> $name"
      eval $__result="'$(cat $file)'"
    fi
  else
    echo "Using var : ${cl_green}\$$variable${cl_reset} ~> $name"
    eval $__result="'${!variable}'"
  fi
}

# shellcheck disable=SC2086
function optional_env_variable_or_secret_file() {
  #
  # Usage:
  #     optional_env_variable_or_secret_file "new_value" \
  #       "GITLAB_CI_INTEGRATION_TEST" \
  #       ".secrets/gitlab_ci_integration_test"
  #
  local name=$1
  local variable=$2
  local file=$3
  local __result=$name

  if [[ -z "${!variable}" ]]; then
    if [[ ! -f "$file" ]]; then
      # NO variable, NO file
      echo "${cl_yellow}Note:${cl_reset} shell environment variable '\$$variable' or file '$file' can be provided."
      return 0
    else
      echo "Using file: ${cl_green}$file${cl_reset} ~> $name"
      eval $__result="'$(cat $file)'"
      return 2
    fi
  else
    echo "Using var : ${cl_green}\$$variable${cl_reset} ~> $name"
    eval $__result="'${!variable}'"
    return 1
  fi
}

function isHelp() {
  local args=("$@")
  if [[ "${args[*]}" =~ "--help" ]]; then echo true; else echo false; fi
}

# --cookies -> "cookies||0",
# --cookies=: -> "cookies||0"
# --cookies=first -> "first||0",
# --cookies=first: -> "first||0"
# --cookies=::1 -> "cookies||1",
# --cookies=:default:1 -> "cookies|default|1"
# --cookies=first::1 -> "first||1"
# --cookies=first:default -> "first|default|0"
# --cookies=first:default:1 -> "first|default|1"
function extract_output_definition() {
  local definition=$1

  # extract output variable name, examples:
  local name=${definition%%=*}
  local name_as_value=${name//-/}
  local output=${definition##*=}
  local variable=""
  local default="1"
  local args_qt="0"

  # extract variable name
  if [[ "$output" == "$definition" ]]; then # simplest: --cookies
    variable=$name_as_value
  elif [[ "$output" == *:* ]]; then # extended: --cookies=first:*, --cookies=first:default:1, --cookies=::1, --cookies=:, --cookies=first:
    local tmp=${output%%:*} && variable=${tmp:-"$name_as_value"}
  else # extended: --cookies=first
    variable=$output
  fi

  # extract default value
  if [[ "$output" == *:* ]]; then default=${output#*:} && default=${default%:*}; fi

  # extract arguments quantity
  if [[ "$output" == *:*:* ]]; then args_qt=${output##*:}; fi

  echo "$variable|$default|$args_qt"
}

# pattern: "{argument},-{short},--{alias}={output}:{init_value}:{args_quantity}"
if [ -z "$ARGS_DEFINITION" ]; then export ARGS_DEFINITION="-h,--help -v,--version=:1.0.0 --debug=DEBUG:*"; fi
function parse_arguments() {
  local args=("$@")

  # TODO (olku): trim whitespaces in $ARGS_DEFINITION, not spaces in begining or end, no double spaces
  echoCommon "${cl_grey}Definition: $ARGS_DEFINITION${cl_reset}" >&2

  # extract definition of each argument, separated by space, remove last empty element
  readarray -td ' ' definitions <<<"$ARGS_DEFINITION " && unset 'definitions[-1]'

  # build lookup map of arguments, extract the longest name of each argument
  declare -A lookup_arguments && lookup_arguments=() # key-to-index_of_definition. e.g. -c -> 0, --cookies -> 0
  declare -A index_to_outputs && index_to_outputs=() # index-to-variable_name, e.g. -c,--cookies -> 0=cookies
  declare -A index_to_args_qt && index_to_args_qt=() # index-to-argument_qauntity, e.g. -c,--cookies -> 0="0"
  declare -A index_to_default && index_to_default=() # index-to-argument_default, e.g. -c,--cookies -> 0="", -c=:default:1 -> 0="default"

  # build parameters mapping
  for i in "${!definitions[@]}"; do
    # TODO (olku): validate the pattern format, otherwise throw an error
    # shellcheck disable=SC2206
    local keys=(${definitions[i]//,/ })
    for key in "${keys[@]}"; do
      local name=${key%%=*} # extract clean key name, e.g. --cookies=first -> --cookies
      local helper=$(extract_output_definition "$key")

      # do the mapping
      lookup_arguments[$name]=$i
      index_to_outputs[$i]=$(echo "$helper" | awk -F'|' '{print $1}')
      index_to_args_qt[$i]=$(echo "$helper" | awk -F'|' '{print $3}')
      index_to_default[$i]=$(echo "$helper" | awk -F'|' '{print $2}')
    done
  done

  local index=1             # indexed input arguments without pre-flag
  local skip_next_counter=0 # how many argument to skip from processing
  local skip_aggregated=""  # all skipped arguments placed into one array
  local last_processed=""   # last processed argument
  local separator=""        # separator between aggregated arguments

  # parse the script arguments and resolve them to output variables
  for i in "${!args[@]}"; do
    local argument=${args[i]}
    local value=""

    # extract key and value from argument, if used format `--key=value`
    # shellcheck disable=SC2206
    if [[ "$argument" == *=* ]]; then local tmp=(${argument//=/ }) && value=${tmp[1]} && argument=${tmp[0]}; fi

    # accumulate arguments that reserved by last processed argument
    if [ "$skip_next_counter" -gt 0 ]; then
      skip_next_counter=$((skip_next_counter - 1))
      skip_aggregated="${skip_aggregated}${separator}${argument}"
      separator=" "
      continue
    fi

    # if skipped aggregated var contains value assign it to the last processed argument
    if [ ${#skip_aggregated} -gt 0 ]; then
      value="$skip_aggregated" && skip_aggregated="" && separator=""

      # assign value to output variable
      local tmp_index=${lookup_arguments[$last_processed]}
      eval "export ${index_to_outputs[$tmp_index]}=\"$value\""
    fi

    # process flags
    if [ ${lookup_arguments[$argument]+_} ]; then
      last_processed=$argument
      local tmp_index=${lookup_arguments[$argument]}
      local expected=${index_to_args_qt[$tmp_index]}

      # if expected more arguments than provided, configure skip_next_counter
      if [ "$expected" -gt 0 ]; then
        skip_next_counter=$expected
        skip_aggregated="$value" # assign current value to the skip_aggregated
        continue
      else
        # assign default value to the output variable first
        eval "export ${index_to_outputs[$tmp_index]}=\"${index_to_default[$tmp_index]}\""

        # default value is re-assigned by provided value
        if [ -n "$value" ]; then
          eval "export ${index_to_outputs[$tmp_index]}=\"$value\""
        fi
      fi
    else
      local by_index="\$$index"

      # process plain unnamed arguments
      case $argument in
      -*) echoCommon "${cl_grey}ignored: $argument ($value)${cl_reset}" >&2 ;;
      *)
        if [ ${lookup_arguments[$by_index]+_} ]; then
          last_processed=$by_index
          local tmp_index=${lookup_arguments[$by_index]}

          eval "export ${index_to_outputs[$tmp_index]}=\"$argument\""
        else
          echoCommon "${cl_grey}ignored: $argument [$by_index]${cl_reset}" >&2
        fi
        index=$((index + 1))
        ;;
      esac
    fi
  done

  # if aggregated var contains somenthing, raise error "too little arguments provided"
  if [ ${#skip_aggregated} -gt 0 ]; then
    if [ "$skip_next_counter" -gt 0 ]; then
      echo "Too little arguments provided"
      exit 1
    else
      local value="$skip_aggregated" && skip_aggregated="" && separator=""
      local tmp_index=${lookup_arguments[$last_processed]}
      eval "export ${index_to_outputs[$tmp_index]}=\"$value\""
    fi
  fi

  # debug output
  echoCommon "definition to output index:"
  printfCommon '%s\n' "${!definitions[@]}" "${definitions[@]}" | pr -2t
  echoCommon "'index', 'output variable name', 'args quantity', 'defaults':"
  printfCommon '\"%s\"\n' "${!index_to_outputs[@]}" "${index_to_outputs[@]}" "${index_to_args_qt[@]}" "${index_to_default[@]}" | pr -4t | sort
  for variable in "${index_to_outputs[@]}"; do
    declare -n var_ref=$variable
    echoCommon "${cl_grey}extracted: $variable=$var_ref${cl_reset}"
  done
}

# array of script arguments cleaned from flags (e.g. --help)
export ARGS_NO_FLAGS=()
function exclude_flags_from_args() {
  local args=("$@")

  # remove all flags from call
  for i in "${!args[@]}"; do
    if [[ ${args[i]} == --* ]]; then unset 'args[i]'; fi
  done

  echoCommon "${cl_grey}Filtered args:" "$@" "~>" "${args[*]}" "$cl_reset" >&2

  # shellcheck disable=SC2207,SC2116
  ARGS_NO_FLAGS=($(echo "${args[*]}"))
}

exclude_flags_from_args "$@"
parse_arguments "$@"

# shellcheck disable=SC2154
# echo "help:$help version:$version debug:$DEBUG first:$FIRST second:$SECOND servers:$servers"

Usage:

# pattern: "{\$argument_number},-{short},--{alias}={output_variable}:{value_if_found}:{expected_args_quantity}"
export ARGS_DEFINITION="\$1,-t,--transaction=args_transaction \$2,-c,--cookies=args_cookies -h,--help -v,--version=:1.0.0"

# shellcheck disable=SC1091 source=_commons.sh
source "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/_commons.sh"

# custom logger
logger calls "$@"

echoCalls "Some debug messages that will be printed if DEBUG=calls or DEBUG=*, or --debug"

# is any help requested
if [ -n "$help" ]; then
  print_usage && exit 0
fi

# is version requested
if [ -n "$version" ]; then
  echo "version: $version" && exit 0
fi

run code with --debug flag if you want to details output

> myscript.sh --version --debug

Filtered args: --version --debug ~>  
Definition: $1,-t,--transaction=args_transaction $2,-c,--cookies=args_cookies -h,--help -v,--version=:1.0.0
ignored: --debug ()
definition to output index:
0                                   $1,-t,--transaction=args_transactio
1                                   $2,-c,--cookies=args_cookies
2                                   -h,--help
3                                   -v,--version=:1.0.0
'index', 'output variable name', 'args quantity', 'defaults':
"0"               "args_transaction "0"               "1"
"1"               "args_cookies"    "0"               "1"
"2"               "help"            "0"               "1"
"3"               "version"         "0"               "1.0.0"
extracted: version=1.0.0
extracted: help=
extracted: args_cookies=
extracted: args_transaction=

latest version in: https://github.com/OleksandrKucherenko/e-bash